Rotating zoom ring
You'd prefer one that wouldn't rotate?
Despite the controversy, I rather like my push pull 100-400. Never had a dust problem... I would welcome faster AF. That's the only downside I have experienced with mine. I would be (pleasantly) surprised if the price is $2400.
I agree - push pull is a very robust design and it is a retrograde step to give us a telephoto like the 70-300L although admittedly that is a good lens optically but is not as tough as the current 100-400 where the front optical assembly slides along a rigid tube.