The main problem facing Labour is that the grassroots movement to keep Corbyn leader is essentially keeping the Tories in power, unchallenged.
Whilst Labour Party membership is at 540,000, those are 540,000 staunch Corbynistas, who are supporting a leadership that is a major turn off to many Labour voters in the rest of the country.
Corbynistas seem to think that as long as they have 'a decent man' as leader, that this is okay and if it means not being in power, so be it.
Everyone else is of the opinion that, well, what's the point of a political party if it's not in power, or at the very least, striving to achieve power?
So Labour will lose traditional safe seats like Copeland, and the Corbynistas will claim everything's fine and an on-track. Meanwhile everyone is bracing themselves for Labour to be devastated in the General Election. By which point it will be too late to rescue, and we'll be at least 10+ years into Tory rule by that point, with another 5 years to follow.
Ultimately I think the party will split, because there's two groups of people with two entirely different outlooks. Compromise isn't in Corbyn's vocabulary and unfortunately, to get into power, you need to compromise.