I'm not sure Martina's ego could handle playing second fiddle to Roger
well, martina played with roger when roger was a nobody then. i am not sure he even won his first title yet.
i doubt they bother about their egos. Hingis once dominated, and now Federar is dominating.
But I am really sure they would not play mixed doubles for slams, at least for now. Federar is really focused in his singles. He does not even want to play Davis Cup first round because he doesnt wasnt to get distracted.
Federer & Hingis would be a great mixed doubles pair. they would probably like go in2 every tournament being somewhat the favourites i reckon. but i doubt they would pair up 4 the aussie open mixed doubles though.
i would like 2 see sharapova & safin pair up together in mixed dubs as well even if most ppl would like 2 see sharapova pair up with roddick.