Namor or Doom. Magneto would work, although I'm not too crazy about it (none atm).
How about no one?
I don't see any other X-women jumping into another relationship so soon after breaking up.
(Not counting Kitty, Storm and Rogue)
She needs to be with someone her own age like Magneto.
Steve is the Cuckoos father but the correct answer is no one.
It's pretty obvious what Bendis is doing, the next time you see Emma Frost wearing white she'll be in a wedding dress marrying Cyclops. This is like House of M all over again.