Which may not be possible. It's far easier, after a turnover of leadership, to say "they were stupid", than it is for a leader to admit, "we were stupid".
I'm not in the UK, and I'm not that current on UK politics, but I think there is a bare possibility that this could happen. It would take a no-confidence vote against May, though, and probably before March.
Mind also that maybe a majority is pro remain now, but there is a notable amount of people who "want control" and by the Brexit vote "finally were heard" (even if consequences are bad it was their free and independent decision!) and where it is really hard to convince them to admit that their vote was "wrong" and tontolarate that other "smart people" in parliament overrule that will of "The People", again. This teaches those people, that voting doesn't matter.
In my opinion from a British perspective the best thing would be the software possible Brexit and then rejoin in a few years. However a soft Brexit isn't in the EU's interest. The EU has to distinguish between member and non-member. (While Norway and Switzerland historically have such complicated in between positions)
The only other way would be Brexiter to admit their failure and a charismatic leader without previous relevance who manages to unite the big divide with a magic wand. But I don't see such a person.