People should remember that a few years ago, before the Cote fight I think, he said he was going to retire after 6 more fights. 6 more years might be pushing it.
He has done a pretty amazing job of staying injury free throughout his career though. I don't think he's ever had to pull out of a fight in the UFC and he still seems very fast and athletic for a 37 year old. He could probably go for another couple years, but I personally hope he retires while he's still on top and we don't have to go through another Chuck, Tito, or Fedor scenario.