Think about it. Irina knew about Vaughn and he himself said that it was no accident that he met Syd when she walked in to CIA. As we know Irina wanted to inflitrate both CIA and SD-6.(which she did succesfully) Vaughn could do both. He got intel about SD-6 from Syd(remember "The Box part 1& 2") and Vaughn could give Irina lots of information about CIA. Also it would make sense if Vaughn's father really was KGB! Maybe Vaughn is Russian spy? What da ya think?