I was standing in Silithus today staring up at that humongous sword and I had a crazy thought. What if they are burning down Teldrassil for tech reasons? (alongside story line reasons of course) Back in the day, they couldn't really render a humongous tree and we got the stump that is Teldrassil in game.
They apparently can render much taller things now. What if we end with a new Night Elf home(either in same location or new one) that actually shows up in game as a tree by the end of BFA? (or beginning of expansion after BFA)