Realistically to win the Tories need to turn out 85% of the people who voted for them last time. Seeing as these people actually voted for the Tories last time, there's a good chance they do so again.
Leaving aside the plausibility of this for now, does it take into account demographic changes since the last GE - in particular "natural wastage" amongst the Tories mainly more elderly supporters?
There's not enough of it to make a meaningful difference over one cycle.
The vast, overwhelming majority of the 2019 Tory vote is still alive and leans to the right. Doesn't mean the Tories will them all of course, but it does mean that it's Labour that has to climb the hill, while the Tories need to turn out their 2019 vote.
Depends what you define as "meaningful". What is undoubtedly true is that since the 2019 GE there has been a significant number of mostly older voters passing on, combined with an influx of mostly younger voters entering the electoral rolls. Of course this happens between all elections, and only has possible significance now because of the extreme age polarisation we have seen in recent years.
Even if it makes only 1-2% difference overall, that might still be enough to swing a close contest.
Wouldn't it be fairly likely that the old who have passed on would have assets inherited by their descendants? Is it reasonable to guess that suddenly inheriting property would suddenly make someone more Conservative?
Then again, the people inheriting might already be Conservative-favoring in 2019, so that would still be a net loss for the Conservatives.