Stewart originally declared his interest and desire to appear in Doctor Who last year when it was announced that he would be appearing with David Tennant in Hamlet this year.
It seems that the BBC are also keen and Stewart is rumoured to have offered a reoccuring part in Season 5, with a possibly character debut in one of the specials.
So, it might all be fanboy wishes but Stewart is on record as saying he'd be interested in appearing on the show and personally more than Patrick Stewart appearing on the show (which I'd love to see) is the fact that if he does play The Meddling Monk it means that other Timelords are out there (well, we already know that the possibility exists because of the appearence of The Master).