Ravving Rabbids and Guitar Hero 3 doing well on the Wii gives me little reason to believe Assassin's Creed would be a success on the Wii. Assassin's Creed is M rated and not a party game. Trends seem to show when a game is released on the 360, PS3, and Wii the Wii version has the poorest sales. I'm not saying that's the case every time, especially if its a game that would appeal to kids.
If more 3rd parties have profited from Wii development I assume we would see more support. Also you have to remember when a HD game is developed it can be ported to the 360, PS3, and PC with little changes. The Wii needs games designed specifically for it or it just shares games with the PS2.
Some good points, but a few things here. Firstly, it is not as simple as a basic HD port from PC to 360 to PS3, as there are licensing costs, GPU compatibilities, etc. PC to 360 is fairly easy, as most PC games are Windows games, so Windows games and 360 games can both use the Direct X technology. That said, it takes a different platform to run the GPU on the PS3, thus making the port trickier. Then, of course, you deal with dev kits, if the company doesn't already own them, and of course, licensing costs, which can cost up to $100K per title. Porting from and to the PS3 is quite its own challenge in itself. Only the art assets stay the same, the codebase needs to change entirely.
It would be reasonable to assume that if a game like No More Heroes can sell over 1m units on the Wii, most M rated games have that potential, Assasin's creed included. There is still a healthy crowd of core gamers that buy Wii games, they just get drowned out in the sales numbers by the amount of casual/part time gamers. There are still over a million people out there that are in the market for M rated Wii games. COD:WaW is a good example of this, as it broke the 1 mil mark, and is on all 3 platforms.