Ashenvale for sure, already pretty contested lorewise.
Southern Barrens already has a horde vs alliance theme so they could defo capitalize on that.
Would be awesome to see them use settlements for these, crossroads, sentinel hill etc.
And this next bit is far out there, but I would love it if they would make these "timed events" like timewalking, and have the end result be affected by things like total score for horde vs alliance, which in turn would determine how that place looked / played until the next time the battle took place again.