I'm glad that it seems like he's extended the longevity of his life by losing a lot of weight. Have you seen him now? Looks amazing for his age. I think if he continued where he was, he might've passed away at some point or be in a worse condition.
He needs as much time as possible to decide what he's going to do after he's gone.
But it's more likely that if Gabe doesn't have someone or something in mind that keeps Steam on track, there's few companies that can buy it. Microsoft could acquire it. Sony could acquire it. Epic games could acquire it.
Companies that would have no care or clue in how to keep Steam as is.
Safest option would be to turn Valve into a foundation, similar to Zeiss: The company owns itself thus can't be bought out, statutory stipulations go along the lines of "Make sure we don't go bankrupt, do great optics, funnel some money to the University of Jena as well as less well off workers in the city". No grand charitable aspirations besides being a good citizen as per 1846 bourgeois values (though that'd be Gabe's choice), otherwise just continue as they've been doing. Make sure all stakeholders (incl. gamers, or at least Valve customers) have standing to enforce those statutes.
That would be nice. Just keep in mind that they already have an arbitration clause, so that seems to piss on (but not all over and certainly not shit on) gamers who have standing to enforce those values.