I don't think there's a very realistic possibility of Vita outselling the 3DS.
The next generation of home consoles...I'm going to go out on a limb and say yes, Sony will eventually return to the top. The PS3, at launch, was an absolute disaster, and it didn't really become a viable console until a good two years later. If the PS4 launches at $299, with a solid launch lineup, it's easy to develop for, and it has an excellent, fully functional and free online service, I don't really see it being outsold by the Wii U.
We know far too little about Microsoft's plans at the moment for me to judge that, but if they try to push an excessive focus on Kinect, I see that falling flat. On the other hand, if they focus on small-scale implementation like in ME3 and Ghost Recon, people might question whether the device is still relevant.
If they can REALLY beef up the technology, and get it to work with large numbers of players who are sitting down, and implement some sort of button system (there is only so much you can do with motion control, as we have seen from Star Wars Kinect and Fable: The Journey), that could potentially be very successful.
I've gone off on a bit of a tangent here, but long story short, yes, I do think Sony will regain the sales crown, and it could potentially be next gen.
(Former) Lead Moderator and (Eternal) VGC Detective 
