#5 - Nov. 16, 2013, 2:08 a.m.
Adventure Mode is still being developed, so please keep it in mind that this could quickly change. Let’s use the example you gave where a character plays through Act I, and unlocks Adventure Mode for that Act. To answer your question, yes, that character could level all the way to 70 by repeatedly playing Act I Adventure Mode, since the monsters would level up with you. I want to reiterate the fact that this is still being developed, though, so stay tuned for more information along the way.