One of the reasons I think a revamp is coming is that I doubt they will have new players continue to go through BFA and SL. Especially not SL if we go back to Azeroth. I really don’t think that SL story will lead to 10.0 the way that BFA did to SL.
So new players will need an expansion to level in that actually takes place on Azeroth, but isn’t Endgame yet. Hence revamp 10-60 and new zones like Dragon Isles for endgame leveling.
Though I’ll admit they could have them just do BFA again because it sets up a bunch of stuff on Azeroth unrelated to SL like the council.