It's all rumors but the leading rumors are.......
Pro-spec body but smaller than the current K-m!
3" LCD, presumably 920k dots
Weather-sealed kit lens (finally!)
More "direct access" buttons - no need to use Fn key any more; flash, drive mode, etc all have direct buttons
"second gen" 14.6mp sensor with lower high ISO noise and even higher image quality (pretty impressive considering the stunning IQ of the current sensor)
Larger and brighter viewfinder than the K20D (again, impressive as the K20D's is considered very, very good for an APS-C sensor)
Video (of course)
Almost certainly full autofocus in Live View mode (LV even gets its own button) and probably more LV bells and whistles overall
Presumably faster focusing
Faster continuous shooting - 6 fps has been mentioned
Far-out rumor but who knows... how about a viewfinder that also can switch to an LCD - so full standard SLR optical or digital (for taking movies, reviewing your photos, etc) - who knows if this'll make it but Pentax does have a patent for such a setup. Sounds pretty great if there are no compromises on the optical side (apparently not based on the more concrete rumors)
Some early shots made it look like it was going to have old-fashioned metal triangle lugs for the camera strap but it's not so clear on more recent shots if this really is the case. It does have a somewhat more "retro" look.
The rumors are flying thick and fast; no doubt it will exceed in some areas and come short in others (there are always "pie in the sky" rumors of things you know won't make it), but the buzz is pretty strong. Hoya has promised fewer DSLR introductions and when they come, they will be serious improvements, not just minor tweaks.
Also, this is apparently going to slot in above the K20D, not be a replacement for it.
I'm going to hold off judgment until we get the final specs, but it certainly sounds pretty exciting. In the meantime, I'm planning on sticking with my K20D for a while; it still works great (better than new, actually) and I'll want to wait for prices to drop a little on the K-7.