oK.. ok...i will sound a little bit silly, but as a MitsuAi spporter i don't like that idea....
Yeah, i think they should develop more her relationship, but in a friendship-haibaramakingjokestomitsuhiko way xDDD and i think they should have more romantic moments, but not seriously ones(well, yes, they need some of them and i would like to see them...) like the one of the Movie 9, funny and cute ^^
http://www.youtube.com/watch?v=FC6QVzVgGv0
or like this one XD
http://www.youtube.com/watch?v=65PehPAGKtk&feature=player_embedded
But they don't need to be dating, only in a Future Special Episode of Gosho Aoyama (i mean...the future of Conan, ran, the detective boys, agasa, kogoro....in a Episode) ^^
Because being serious, Mitsuhiko and Ai Haibara dating is very impossible with 6 years old D: But with 14-17 years old yes xD
EDIT:
New cute pic ^^: