Are you just floating this or is there actual evidence of this being the case on beta? I'm not following mages, so if this is what it looks like and you have proof of that just PM me and I'll un-shitheap this post. If this is not what's in the please don't speculate about maybe possibly there's a chance that something will be like it once was. That's just too much iffy in the air crap and doesn't really add anything.
Maybe the rotation wont be just 3AB-MBAR or 4AB-MBAR. and it will be closer to what we had in TBC where spamming AB to a point will be a good thing and you will need to learn what is that point.
So you will do 8AB-MBAR at times if you have the mana but will risk your mana bar depleting and on other times you will do 3AB-MBAR for mana regen or some form like that.