I doubt there will be level caps in acts.
That defeats the purpose of true D&D - it´s up to the players how to play the game - some will meticulously look through everything, some will "speed run it", however, MOST will be somewhere in the middle.
Personally, I love games where you have access to foes that are way beyond your capabilities and you will have to return when you are equipped to manage them. It that way you get freedom to plan and play more freely, even in a linear game style..