Things I like that I hope make it to the next iteration of APS-C cameras:
1) They moved the "select AF point button" to a place that your thumb can more easily reach. After over two years of owning the K-3, I still haven't worked my brain around their placement on the bottom right of the body. Silly. Good move with the K-1.
2) A lock button on the left side of the body. I don't have too many issues hitting the RAW/FX button on my K-3 during warm weather, but in the winter I easily can toggle it while wearing gloves. The fact that there isn't any way to simply disable this button is beyond me. Very much something they should incorporate into a firmware fix, IMO.
3) I like that they did away with the video/still switch and the live view "red button." Again, AF button and the digital playback button being put where your thumb can easily reach is a step in the right direction.
The only change I'd still like to see is an alterative method of selecting the metering. I liked the physical switch on the K-7. Using a button and e-dial is rather slow in my experience. I'd like to see the RAW/FX be able to handle metering, where you could hold down the RAW button and it would switch to either spot or center metering (one would choose which it would toggle to in the menu) as long as you held the button down. It wouldn't completely switch your metering mode, but would offer a nice way to check metering without needing to do anything more than use your left thumb.
As far as specs/capabilities go, I really hope that they pioneer a simple and effective way to connect the camera to phones and other devices. Tethering is a must, as would be an easy to use file transfer system. If the screen is a touch screen, one could conceivably hold a phone or other device close by and drag or swipe photos "onto" the other device straight from the camera. That could be nice!
edit- any and all customization of buttons and switches would be great, IMO. For example, the K-3's "movie and still" switch should be able to become a "AF point selection" on/off switch. The little icon on the back wouldn't change, but user friendliness would. Any way they could make the device more intuitive for the individual is something I support!