It should do well. When advertising ramps up closer to launch, I think we're going to see a massive (for the franchise) bump as well. Plus, I think a lot of MH's 200k or so dedicated fans will jump on board too, in addition to general Wii gamers.
The demo seems to be helping a bit already, Nintendo should consider doing the same for some of their more under-the-radar core games (like Sin & Punishment 2). Only not at GameStop, go with a retailer who'll actually distribute the demo as promised (or better yet, all retailers). Tri preorders could be even higher imo if GameStop actually gave away the demo rather than hold it hostage as a pre-order bonus (against Capcom's wishes btw). Giving it to people who pre-order is like preaching to the choir, it's the people who aren't already interested in MH that the demo needs to reach most. :/







