If you look at the
K-S1 report on the front page, there's a video where they scroll through the menus of a K-S1 on the show floor at Photokina, and you don't see Interval Shooting or Multi-Exposure in the options there. That's a pre-release firmware, as far as I know, so it might not be indicative, but since it's not in the manual either... I've not used interval shooting yet, but I
have used multi-exposure many times "in lieu" of an ND filter, and it's a very useful feature. I've also admired other's work in shooting timelapse, including with the K-01, and have been thinking about trying it myself. I thought Ricoh wasn't pitching the K-S1 as entry-level camera? Removing features that are in previous generation models - even the K-500 has interval and multi-exposure, right? - definitely would make the K-S1 seem pretty entry level. We'll know for sure once it ships, I guess...
EDIT: It occurs to me that in the K-3 these options may have moved, I think, away from the general camera menu and into the "drive-mode" settings (where you choose between single, continuous high, continuous low, and so on). In the PF video I linked to, that button is not hit. So maybe there's still hope.
EDIT #2: If you look at the Pentax Web Store's
page for the K-S1, under specifications, it
is listed under "Drive modes":
Multi-exposure: 2-9 shots, auto exposure adjustment
Interval: 999 shots, 3 sec to 24 hr interval, time delay
I'm just not too confident of that as an authoritative source...