I think the main question is whether Johnson resigns before or after the Tories get annihilated in local elections in May
Polls already tightening although Labour still about 5-7 points ahead. One problem with local elections is turnout tends to be terrible which is good for Tories. Amongst older voters, Tories still have big lead while as usual Labour massive amongst millennials. Real change since 2019 is Gen Xers who Tories won by over 10 points, but are now trailing amongst. But I suspect if Johnson cannot regain lead by summer at latest party dumps him. Most don't expect him to win as big as 2019 as Keir Starmer far harder to scare people as opposed to Corbyn and Brexit is done so many in North & Midlands who voted Tory just to get Brexit done but don't support them on other issues are probably gone.
But thanks to age demographics and also Tory vote more efficient, many still believe they can come back with him, but if polls don't improve they will dump him as winning is what matters most.