I think that this isn't a coup but a protest. They know he will be voted back in again. But they have nothing to lose- a lot of them will be annihilated regardless of who is leader at this point I think- they are making a stand so that their reputations can be salvaged after the coming storm.
Viddy, above is right, I would like for there to be some continuation of Mcdonnels current economic path, but I think the price of Corbyn being leader would be far too steep (as great as it may be, it won't matter a dime if it doesn't get realised).
Ideally we should have Corbyn's first shadow cabinet (when he was elected) returned and Corbyn should step down and make way for a more pragmatic and less tainted newcomer.