Yes, I've already thought about the next gen. That would be a refined Wii-type remote with much more accuracy and very low latency. Dedicated hardware in the console specifically geared toward 1:1 monitoring of the remotes position in space regardless of how fast or wildly the person is shaking it... Point and shoot is a winner -- even over the PCs mouse/keyboard combo.
Graphics power needs to be that of the current generation -- 720P HD with solid texturing, bump mapping capabilities and very, very powerful 4XAA without the CPU/GPU taking a hit. The console needs to be able to accomplish 720P 60FPS without breaking a sweat and without developers having to squeeze every ounce of power they can out of the console.
Outside of those, a storage medium like a hard drive is necessary as I love demos. It probably needs to be bigger than the current gen systems as downloadable content is going to become more important.
A low cost high-density disk player. I don't think it needs to be an industry standard like blue-ray or HD-DVD -- it just needs to store more than current DVD9 and be Quiet, Fast, and *CHEAP*. By not using an industry standard, they can avoid royalties and keep the cost down to some degree.
All this needs to happen in a $299 package for mass adoption to begin quickly. I would help if it came from one of the current Big 3 and was fully compatible with previous gen games as that would give it a library of games to play right out of the gate...
This, in my opinion would be Nintendo's greatest move if they were to make an HD Wii that plays all current gamecube and Wii games as well as is a high power console going forward...
I hate trolls.

Systems I currently own: 360, PS3, Wii, DS Lite (2)
Systems I've owned: PS2, PS1, Dreamcast, Saturn, 3DO, Genesis, Gamecube, N64, SNES, NES, GBA, GB, C64, Amiga, Atari 2600 and 5200, Sega Game Gear, Vectrex, Intellivision, Pong. Yes, Pong.