Re: should batman appear in the MOS sequel?
I agree, Sharkboy. I think devising a story that suits both characters' strengths is the key. It needs to be a global threat with some kind of mystery/espionage element, and Batman's cunning should be an essential component in the denouement.
As for the DC/Marvel thing: Marvel farts out a movie every week, so the promise of yet further installments can hardly have the same impact as a Batman/Superman double ticket.
Difficult, difficult, lemon-difficult.