Phil did say in his podcast (episode with Rob & Brennan) that the idea isn't too far-fetched. We have a pool of 31 teams to choose from, and if enough of them can be available during the month of filming, we could have an interesting cast, especially since some winners aren't exactly Alpha Teams as some people put it.
My 11 Choices for Winners/Victors Edition:
Rob & Brennan (gained new appreciation for them from interviews more than a decade after their win)
Flo & Zach (although I don't think Zach can join the Race anymore since he's tied with the production or something?)
Chip & Kim (another popular choice, apparently)
The Linz Family (two of them of course)
BJ & Tyler (due to popular demand, though I don't actually like them)
Tammy & Victor
Nat & Kat
Ernie & Cindy
Josh & Brent
Amy & Maya
Brooke & Scott
2 or 3 MM, 2 FF, 5 or 6 MF and 2 Family, 6 Friends, 3 Couple teams
Here's the thing, these teams' story lines were pretty much complete by the end of their respective seasons. Bringing them back seems kinda redundant seeing as they got their "happy ending" already. That's why a First/Early-Outs season or Unfinished Business season for me is much more compelling. These teams either didn't get to Race that far, and will still get to experience the new aspects of the Race is it went on OR they have more to prove this time round. Second Chances season is what I want to call it.