Ohdear, I do not quite trust them remaking the old levels again, however if it turns out like Green Hill Zone in Sonic Adventure 2, I'll be all for it, as long as they can carry over that style of level design and not the ones seen in Sonic Unleashed and Sonic Colours recently, it's a real wonder why they do not try to make levels like that again, I would consider the Green Hill Zone one of the best 3D platformer levels, I can't fathom why they did not carry that over into Sonic Heroes, even with the three character partnership (If anything, the level design would have suited it much better)
Mario & Sonic 2012 will probably be much better than the previous titles, since Mario & Sonic 2010 was much better than the last one too.