I did some searching and from what I've read the answer is it will not be included. The answer why varies depending on who you ask and most of them don't make sense minus these two exceptions which I can understand.
More animation work. They'd have to come up with strafing and backpeddling animations and possibly variations of any ability that can be used why moving. The second reason being balanced. Having full directional movement while being able to attack gives ranged a huge advantage over melee in addition to the normal advantages of range. Now this could be worked around if all ranged abilities required you to stand still anyways but that could limit ability design options more than the developers want.
