It would be good in quite a few ways for the sport, not too mention the sheer amount of publicity it would bring if he were to make this 'sensational' return.
Personally I've never really been a Schumi fan but I would love to see him make a return, it would just make next year even more eventful.
But somehow I really cannot see it happening, he's too loyal to Ferrari. He wouldn't even drive half the ROC cars nor would he drive the reasonably priced car on Top Gear because they were not Ferrari's .. So that's why I really cannot see it happening.