The Tories are already descending into arrogance, as witness the trouble caused by the so-called "dementia tax" where it would have been so much less controversial to have continued with the current testing but introduced a social insurance scheme. I can see this idea being dropped or modified.
However, the problems Labour face are not simply those of a party facing a heavy defeat in the polls: such defeats usually happen after a period in power. Labour will have been out of power for 7 years (it was only 4 at the cataclysm of 1983) when it in all probability goes even further backwards in June. One difficulty is that it is saddled with a system that gives too much power to people who are completely out of touch with what is needed to win elections. The tradiutional base for labour is shrunk and or divided. The Tories are eagerly, some would say cynically, gobbling up territory on the swivelling UKIP right (hard Brexit) as well as pushing into what remains of labour territory (state intervention is good), pretty much as Tony Blair did up to 1997.
(And possibly ignoring the bit in the middle for now as I alluded to earlier). What will come of that is unclear, but art the moment the danger for Labour is that many of the moderates will see little prospect of wresting the battle of ideas away from the hard left. There are effectively two labour parties fighting it out at the moment, as you can see clearly from the discord between the defence spokesperson and the shadow home secretary, leaving Corbyn floundering uselessly in the middle.
One good thing about Corbyn is he is a great campaigner, but his adoring audiences seem small in the grand scheme of things, and he seems unlikely to grow it much