Once Hatton gets destroyed by Pac he will want to cash in on a Khan fight as soon as possible. Hattons options are pretty much closed after the Pac fight but he should still have a good enough name to be able to pull off a Khan fight. Khan and Warren are very shrewd so they may want to pick up another good name for his record before going for tough tests at light welter and above. I can see this fight happening early 2010 or maybe even christmas 09 if Hatton is back to fitness by then after his beating.
Hatton would kill Khan right now. Khan is 22 still learning the game, Hatton is 30 prime top fighter.
Hatton's not planning on fighting Khan, as he's planning on beating Pacquiao and finishing his career with mega-fights with the top names - Marquez, Valero, Campbell, Bradley, Mayweather, Cotto and Mosley would all want him. If Hatton loses to Pacquiao (which I think he will), then fighting Khan for the WBA title (providing Khan beats Kotelnik) at Wembley Stadium suddenly becomes much more viable.
If (Probably a WHEN) Hatton gets beat off Pacman. He will get knocked out by ODH later this year at Wembley. Mark My Words