I would be incredibly surprised if they include the Wii chipset in the Wii U, as it'll be completely unnecessary. The Wii U's CPU is an IBM designed Power architecture chip, just like the Wii's CPU. So long as it is capable of out of order execution (quite likely) and has an AltiVec unit (almost certainly), hardware backwards compatibility should be almost trivially easy on the CPU. Even if not strictly binary compatible, the CPU will be more than capable of handling software emulation. Similarly when it comes to the GPU, it's an AMD chip like the last one, and will either include TEV functionality for hardware BC or emulate it in software relatively easily. In neither case is an identical copy of the Wii's hardware in any way necessary.
This is largely academic, though, as Nintendo have said that Wii games will run in standard def. This would probably end up being the case either way, as many games have resolution-dependent effects, such as the wonderful DoF blur in Skyward Sword, that would cause problems for any attempt to render Wii games in HD.
On the question of charging for HD versions, I actually wouldn't mind if they released HD collections of Mario games, Zelda games, Metroid games, etc. so long as they put in the effort to create HD GUI elements and add touchscreen functionality for inventories in Zelda games, etc.