The most probable choices would be either Sakura or Karin, though with the latter one the percentage has lowered drastically with the recent manga events (he tried to kill her, as he did with Sakura but failed on both attempts). And I think, it he ever becomes sane again, he would choose Sakura because Sakura, no matter how much she tries to forget, still has feelings for him.
posted over a year ago
he will choose sakura coz karin will pick suigetsu
I think that he will make up with Karin and revive his clan with her. Their kids will have both Uchiha and Uzumaki blood in them and would be very strong.