"They" now means Harman. Sure anything can happen but I don't see Roon under Harman going anywhere soon. Maybe you're in a different situation but the only time I'm without an Internet connection at home is when all power is out which is a bad time for hifi listening generally. In those circumstances, or on the road with no connection I can rely on the 1TB of flac on my LG V60.Which means it's a rental service, if they go under you have a useless $800 cost, or the months you've paid for it and no longer able to use it in the future.
Unless if they go bust and release a "offline version" which I doubt. Nor is it open source, so unlike LMS, support will end
Ideally Wiim app/firmware should be open source also