They won't. Projects like Atom and VSCode thrives because they have big companies behind them. Remove them - and the project will die.
There are tons of abandoned text editors on GiHub.
Of course, with a team backing the project that changes the dynamic a bit
Of Coz it wont be a small amount. It could be 25,000 copies. But then lot of companies, whom may like Sublime, could spend and join the race.
You're not loosing any income - honest people will continue to buy the license, and those who are not honest or cannot afford it will continue to not buy a license. But people will be put at ease about the bus factor. We will learn a lot about how to produce a snappy app with a multiplatform toolkit. And I'm sure people will contribute back great features.
I'm curious as to what your evidence to back this statement up is. As is, most donation-ware ends up getting next to nothing in donations.
Have you ever considered open-sourcing SLT? This is your only route to immortalize this amazing piece of software. I'm sure you'd receive immense community contributions and widespread support. If you switch to a donation model + enterprise support plans, I think you're likely to earn greatly more than you currently do.
I love SLT and have used it throughout my career, but I still feel more comfortable depending on Atom because I know it will be supported by the community in the event that something bad happens with the ownership. If you don't open-source SLT, I sadly believe that open alternatives like Atom will outlive it.