Yeah...not gonna happen, Lars and Alisa are DEFINITELY appearing.
This world is in the timeset of SF4 and Tekken 6, (T6 timeline as shown by Jin being the leader of the Mishima Zaibatsu), and SF4's main character is already in the game (Abel), so it makes perfect sense to include Tekken 6's main character, Lars. And of course, you don't get Lars without Alisa.
Plus they fit the whole tag team thing they're promoting so yeah...no chance in hell they aren't in.