If Corbyn stays as leader of the Labour Party (which I think is most unlikely) it would be the end of the party.
More likely is the far left would put up a candidate to replace him, although as far as I am aware new nominees still need to be proposed by MPs.
Who's to say that instead Britain won't get a UK version of En Marche! to challenge Mme Le May?
Corbyn will be 68 by election day. Assuming the next parliament lasts the full 5 years, he will be 73 by the election after that and 78 by the end of that parliament. Assuming he became PM in 2002, would he expect to serve the full 5 years as PM or would he retire part way through and hand over to an unelected someone else? I inserted the "unelected" because Teresa May was accused of being unelected by some, particularly Labour supporters.
I was trying to make the point that, if Labour don't get elected next month, he would be wise to stand down as leader and give someone else a chance to prepare Labour for the following election.
What I can see happening, as the Independent link indicates, is that Corbyn would try to hang on until the party conference in the autumn, when his supporters might try to get the leadership election rules changed to allow a far left successor to be selected by MPs.
What might happen in that intervening time is anyone's guess.