I think it's only a matter of time before we see it. I say the fight happens within the next year and a half.
Soon, but possibily a catch weight. Silva has mentioned that he would go down in weight class rather than fighting in 205 as an insinuation that he feels GSP poses the biggest challenge. You know what though let GSP enjoy his hard earned victory and clean up a few more contenders namely Jon Fitch and possibly Alves or Sanchez if they make it to title contention. Then GSP will have officially mopped up the WW division if he hasn't already and so ends the "Rocky" story. In Rocky the main character wasn't half as arrogant. Perhaps it's time for Serra to reflect on everything. What a great finish by GSP!