I still believe there will be a partnership with valve and the PS4 will essentially be a steam box. With valve dumping a lot of their hardware developers and with the release of big picture mode and Sony seemingly turning the drm over to whatever the developers wish, steamworks working with the PS4 makes total sense. Additionally, the PS4 is more like a PC than ever before and you can already sync up accounts with Steam on the PC/PS3 so it's just an extension and a deepening of the relationship.
Plus, Sony has been gunning to make sure a lot of the indie development engines are available and working for easy ports from PC to the PS4. I think a partnership with Valve and the self publishing options for developers go hand in hand with all of that. On top of this, we are seeing a much bigger resurgence of developers pushing for PC ports, especially Japanese developers and, although this is pie in the sky, steamworks versions unlocking the PC, PS4,and possibly Mac version if available, would be a big deal.
For Vita, I think the big definitive handheld get which would provide the best control by far, and way better than on a touch screen, would be Minecraft on the vita. That game is still huge and I think putting it on vita makes perfect sense.
Probably all wrong, but just makes sense.