a) Within the university, I don't see them going away, because a lot have tenure and universities aren't subject to the brutality of market forces as much as private sector. (They're not totally immune either, so when budget cuts come I do think some of the DEI positions will be the first to get cut. The positions will get cut, but the faculty staffing those positions will likely remain on faculty.)

b/c) I think they are losing influence. I've seen more and more people get comfortable speaking out openly against DEI. At first, it was fine to pay lip service when it didn't affect operations too much. But I think they pushed too hard and now people are pushing back. At my own institutions they introduced some really insane and productivity-hampering hiring policies and many departments are quite upset about it, including my own.