This is a good comparison. GWS dies, 40k either is better or... turns into horrendous mess when some company that has no idea what to do inherits Wh40k. Though, tbh, they would have to be really bad to beat GW.
I mean 40k is a big IP and its got high-potential too, give it to most any company and it'll be much better than it is now.
.....no.
GWS is a big IP of a different age. That's why so many people still play it, read it, enjoy it....because it's stayed relatively timeless. Oh sure, they added Tau and WHF is starting to get stupid. But 40k has insulated itself from a lot of what's become modern and popular, and refused to really change more than just the story. It's a strength of the IP and a weakness.
Giving it to a new company with a motivation to make it popular again would entail changing half of what GWS has intentionally kept static. New themes would be introduced (love, fun, happiness, sex, new races to fit someone's marketing agenda, an alternative to grimdark that some dork has been begging for for years so canon will reflect their fanfic.) There are few to no companies I would feel comfortable taking on 40k, and fewer still I think would actually do it justice or understand what's made it work in the past. Selling 40k would be about what's good for shareholders on both sides, not what's good for the IP. You can already see this happening in the way being licensed out for video games.