As the above posters noted, it seems unlikely they would make changes to the current classes as drastic as, say, removing one of them entirely (because if the Vanguard gets cut, I will most certainly go nuclear on something. Also, PREORDER CANCELLED HRRRRNGH). But I think that it would benefit from the ME3MP experience in terms of changing things up, as regards abilities and their variety with respect the individual classes, for example giving you a choice of powers previously unavailable for the class (biotic bubbles have been mentioned).
Personally, I can conceive of something like a wider - branching skill tree for each class, where at certain level mark, an adept, for example, would be given a choice between getting the barrier power or the biotic bubble, but would not be allowed to have both (just an illustrative example, folks). Ultimately, you would end up with two different characters, both technically being an Adept in class, but having different sets of abilities and powers.