possibly best to wait till may before consulting the crystal balls though eh.
i doubt May will give good indications....
personally, i think it will be like the last electoral cycle - i think that people will vote Labour in council and EU elections, as well as by-elections, i think people will say that they like Corbyn and his economic policies (i do..), and i think that it will all look a bit tight going into election day. on the day however it will be different, with Labour getting hammered in the potential swing seats in the Midlands and South that it needs to win to get anywhere near forming a government, even a coalition with the SNP. Corbyn excites some, but
broadly they are those within seats that are already Labour/SNP seats, the people he really turns off are in seats he needs to take from the tories.
that does not mean he needs to (can?) take votes from the tories, but it does mean that where he picks up votes in those potential swing seats from those who either don't vote Labour, or just don't vote, he's also mobilising those who are deeply hostile to him to vote when otherwise they might not, or to vote tory when they might otherwise have voted UKIP.
much will depend on so many variables like the EU referendum, the tory leadership, the economy, and yes - to what degree the Labour party tears itself apart. ask Micheal Foot or Neil Kinnock about elections that should otherwise have been theirs for the taking..