I think a power level between Wii U and XBox1 is more likely, and I'd be fine with that.
I've been very impressed with what they've achieved moving to HD with the WII U and I'm certain another good boost in power will be enough for them to easily deliver good experiences.
Its clear that they are going to have to unify the game development for the handheld & full size console - it looks like they are in the position where they will have to do the heavy lifting for the software on their platforms themselves (at least until they can establish a decent user base) - and this gen has shown they struggle to do that for 2 platforms at once. The WiiU's early life suffered terribly from them going all out to make a success of the 3DS and the console never really recovered.
I don't think that's necessarily going to mean a single machine though. That would mean expensive dual-purpose hardware. With either bad battery life on the handheld, or lack of power on the home console.
I think instead, they'll both be based on the same architecture and recieve the same games but it will be like 'low' and 'high' settings on the PC, where the home console has higher resolution, higher res textures and more fancy effects and shaders.
If they have any sense, it will be 1 purchase to use the game on either or both platforms.
This will solve a lot of problems at once: They can offer their full library of games on both, they don't have to compromise either console, they properly support people who only have one machine or both, they can keep the costs low (relatively) for both.
Finally, I hope they choose an x86 platform for both machines so they make life as easy as possible for 3rd party developers to port/ co-develop their PS4 XBox 1 games. I've got a fairly powerful PC and a cheap tablet and both are based on x86, so the full range of hardware exists and is practical on x86.
I'm quite up for them offering new features, although I could do without new controller gimmics this time round. That said, I think they can and probably should include gyro and some kind of touch on both machines - like the PS4 consolidating the controller innovations of the last 10 years so they're there for when it makes sense to take advantage of them.
