Capcom’s Yoshinori Ono has confirmed interest in a Nintendo x Capcom fighter. At the Nintendo 3DS conference in Amsterdam yesterday Ono was posed the question, “considering you are trying to make Street Fighter IV 3DS accessible to a wider audience, did you ever think about including Nintendo characters to broaden the appeal?”
It was at this point that he confirmed interest in such a crossover and said that the idea should be pitched to Nintendo of Japan and Masahiro Sakurai.
[Source]