Maybe, but you can as well use argument that it would be easier to do squish and world re-scalling first (as foundation) in 8.3.5, get rid of bugs between 8.3.5 and pre-patch (it's rather dead period of expac, but it would be far better data than PTR), then implement class changes in 9.0.
AFAIK number of talent rows stay the same, all they have to do is cut required level for each skill in half (right now you get new stuff on levels 1-100, after squish it would be 1-50).