Galaxy will definitely hit 10m units sold. It is only 3.6m units away, and it has years to sell. If we assume it takes 2 years for it to hit 10m it only needs to sell ~10k per week to pull that off. Currently it is selling at ~80k/wk.
Mario & Sonic is a long shot, but it also could sell 10m units. It currently needs 6m units, and is selling at ~90k/wk. For it to hit 10m in 2 year, it needs to average 57k/wk, which is possible, but a long shot.
Big Brain Academy: Wii Degree could make 5m, but it will take at least 2 years, probably closer to 3.
Guitar Hero 3 probably won't hit 5m due to newer versions killing it off.
Mario Party 8 will also be killed off before hitting 10m.
So essentially, I think there will be at least 7 10m, and 10 5m sellers.
As for unreleased games, The 2 mario party games from now could break into the 5m again. I doubt the next version would sell as well, but 2 versions from now might. I'll make more guesses once E3 happens, but for now, we don't have a clue what is coming to the wii.