I sincerely hope that Hamilton knows what he has done here. This move can not be compared to schumacher move to ferrari (1996). Teams are much more close now and importantly testing is banned (except YDT). Ham would be mad to not have a performance clause in his 3 yr contract.
If the team fails to show improvement in next couple of seasons (which i doubt) he should go to Redbull in 2014 (vettel to Ferrari, as being predicted by many).
As for MSC its embarrassing as a fan to see all this happening. But it might have been planned before. Only MSC knows the truth. Would surely not like seeing him in a sauber next season, maybe ferrari or lotus if he wants to continue.
If he has decided to retire than lets enjoy the remaining races as Brazilian gp may be the last time we witness this great champ

Hope he drives they way he did in brazil 2006 for the rest of the season and achieve what he came for. A WIN!!!!!!!!!!