to answer your question, yes wolfe will be the starter for northern illinois at tailback. but harris is certainly going to get his carries.
that being said, i wouldnt think twice about drafting wolfe.
keep in mind, northern illinois runs the football more than any team in the mac, and (aside from your pure option teams like navy and air force), they also run it as much as anyone in the nation. youre not talking about dividing up 30-35 carries between two guys. theres games where niu runs the ball 50-55 times, so there are plenty of carries to go around.
with their quarterback position unsettled, theyre likely to pound the ball even more.
their coaching staff is also talking about keeping wolfe on the field as a slot receiver at times when harris is in the backfield, so fantasy-wise, you can still get some receptions from wolfe as well.