From what I can tell, the option to use New or Legacy is still present. With that being said, if regrets are had, I guess I can always switch back to Legacy. However, this would be backwards progress in terms of product enhancement.
I would recommend that you "switch" over because you can literally just test out 2.0 and then switch back if you want.
Caveat to this is: Do not edit Email 1.0 emails after you switch as they will automatically switch over to Email 2.0.