I could see a hybrid of sorts. LIke if your at home your system gets the game in 1080p, but if your on the road it drops to 720p or something.
Essentially think of the Wii U. The tablet is the handheld console and can be played away from home, but when at home it syncs of with a console like the Wii U does and gives it more power to tap from.
Obviously the Pad needs to be smaller I woudl say for more portability. But I would love an idea something like this. Be nice to have to not have to get two consoles and just buy one.
ONLY problem I see with this is that as dominant the Nintnedo handheld market is, I don't know if Nintendo would risk that by making a hybrid that might confuse consumers, or be too expensive.