K-s1: what do we know 'for sure'?

On the Ricoh Japan site, we know this -
2014年9月11日までにご注文いただくと、発売日（2014年9月26日）

Other sites say shipping in September, so the 9/26 date seems more likely than the 11th - especially since it's the 12th now and I have no confirmation e-mail :^(  Originally the blue/white/black were supposed to ship two weeks earlier than the other colors, so these might be correct ship dates - for Japan!

 edit.. the translated page says 'Come out in 2014.09.26'

Given that it's hard to reshape a camera body, we presume that the sensor, SR, button availability & layout, and other hardware bits are well-known quantities.  Oddly we haven't heard the shutter fire in any videos, so some of the inner hardware is still a mystery; will it be fairly K-5 silent, or more K-50 'clacky'? 
Edit - Adam at pentaxforums says it's very much a K-50 clack, not a K-5 swoosh.

So what's on 'paper' from Ricoh?

• A new 20.12Mpx sensor (let's call it twenty) for a pinch more resolution and cropping relative to the sweet-16 sensor of past models, a pinch less than the K-3, and reviews (of Sony cams) that show it to be a good performer.  It's noteworthy, a slight positive in my Book (and I'm glad it isn't 24M) so some joy but overall to me: no big deal.
• Size: for the specs this is a small and light camera, like a melded K-x mark II and a K-01 mark II with a few good K-3 parts within.  For me small is good, and my search for a small camera with indifferent small sensor ends now!  That IS a big deal to me, and I'm happy to see it.
• Weather Resistance: nope.  The price I seem to pay for smaller size is battery and WR.  I have a K-5 for wet shots though, so as a primary camera this one is just fine.  The control ring on the back means less entry points for mist on top anyway - and like most intergalactic hitch-hikers I know where my towel is!
• Li-109 battery, weaker and smaller than recent flagship cams - oh yeah this Isn't a flagship!  I can carry a spare, and I did anyway with the K-5 - so another note without complaint.  We film veterans used to go about 38 shots max before having to open up the camera, so making a battery change around 400 shots isn't really that bad :^)
• ISO 100-51200.  Several early reviewers say 102400, implying iso expansion or perhaps early firmware - but again, 'subject to change' applies, and as I type Ricoh says 51200 max.
• AF features are similar to the K-3 with AF expansion and hold functions - BUT Safox IX+ means fewer actual points, and no word on f/2.8 sensors.  Focuses to EV-1 not -3 so low-light skill is not up to K-5ii or K-3 models.  AF-A shows on the rear screen shots, so that's either a menu thing or another firmware question-mark; the switch on the side only does MF/AF and the K-3 choose-which-AF button is not present.
• One control dial.  Yes, a tragic loss - oh yeah some of my best images were taken with the K-01, K200d and Sony A200, all 1-dial cameras.  Worse yet the 2-dialers often find me spinning the wrong one (yes that's on me, I should change the way they operate.  I continue to seek My Answer on the K-5!).  So again, noted but not mourned.
• Settings dial is on the back!  And it lights up!! OK, what's wrong with me, I should be upset and all fired up - but this is fine by me, as I've heard that the lights can be turned off (but do we know that 'for sure'?). I hope I can keep the shutter LED light on though!
• Video is on the power switch and the LED lights red in video mode, green for stills.  This will be valuable to users I know (there's one in my mirror) who take very short videos unintentionally!
• PRIME M-II sensor processing.  This is a mystery that only time can resolve.  The PRIME M came with the K-01/30 intros, but the only visible change is that the video is now accessed by the power dial.  Ah, the 640x480 setting is gone too, maybe that's part of it?  Some day we will know what this means - or maybe not!  The M-II does give us compressed video with good specs, focus peaking (yay!), interval movies (not compressed!) and some other things I probably didn't notice when I owned my K-01.  Video isn't a big deal to me... yet I keep thinking it will become interesting again; in the late '90s I backpacked for a week with a DV camcorder AND an SLR, so video has been big before!  Edit: Since the pipeline went two directions with PRIME M and PRIME II, maybe all future cams will use the M II as the latest and best reunification of the component - that makes enough sense that it could be true!  We also wonder if video bit-rate quality is adjustable now; time will tell.
• The flash is a bit weaker, guide number of 10m not 12.  I often throttle back on flash to keep things more natural so that's noted but not significant to me.
• Full viewfinder, nice screen, and the usual DSLR features like a hot shoe.  Check!
• Green button, Sv, TAv, -10°C operating minimum, and other Pentax special touches.  Hooray!
• Strap lugs holding the strap to the camera, Not jingle-clips like the K-5 models have.  Thank you, thank you!
• Misc. and sundry updates include UH1 and FluCard capability, rotation-axis SR (which allows for AstroTracer with O-GPS1), multi-auto WB from Ricoh and K-3 products, and ?14-bit RAW files.   The ? is because specs show 14 and 12 bits, so that's another unsettled parameter like ISO max.

I think that will do (I don't find fonts worthy of a bullet, so there).  I added a few things that aren't clear yet: ISO range, shutter sound, and in fact everything about the firmware other than a font change.  

I downloaded the spec sheet and highlighted changes from the K-5, and many purple items are in there.  Many other features are on the K-50 but some are not, suggesting the answer to many people's question
"why buy this when the K-50 is cheaper, has two control wheels and WR??".

Or just go with the easy answer - We are not all the same.

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Edit: the Ricoh page has been updated as of the 19th and more has become clear.  Only 12-bit raw is referenced now, and additions made to include AF adjustments similar to recent Pentaces.  I see playback editing includes moiré reduction, that's new to me but was probably on the K-3.  Also seen now are 'slant correction' along with different aspect-ratio crops, and all the lens corrections and custom images are here.  It's still unclear if saving custom settings is possible now; no C1/C2 setting on dial or USER option seen anywhere.  Like the K-3 it comes with the new Pentax DCU5.x software, still based on SilkyPix but a later version.
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Update.. Photkina 2014 is over, and hands-on reports are better than visual 1st impressions.  Firmware 0.3 was on test cameras and iso102400 was 'available' though no keepers were allowed.  For a camera due out in a week the firmware seems quite unsettled!
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Final edit / K-s1 update, 27.Sep
Given the ever-changing specifications online, and a bill that I did not expect, I have canceled my order.  While examining cheaper options I encountered a barely-used K50 in white for half the price of the K-s1.  Since I have the WR kit lens, and since the K50 has all the items that appear to be removed or unmentioned for K-s1 specs, this cannot be passed up.  Now the K-5 can go into the shop without worry and I have focus peaking and compressed video like my old K-01 but with a real viewfinder.  I hope the K-s1 does well without me, as I shall do without it - and the expense of it.  When Pentax can access Sony's sensor with phase-detect AF points I'll probably go shopping again.