Hubitat originally planned to launch "premium" services for a fee. That plan was scrapped, but it may be proposed again in the future (see here, among other posts from staff: Premium Services). I don't think there's been any statement since as to why this plan was changed or if there's a good chance it will be actually offered at some point. In either case, the original plan was for these to be just "cloud extras," with the hub continuing it work in every other way with or without them. (I can't remember what they were thinking of offering, but considering they do have a cloud endpoint that requires ongoing maintenance and is used for things like cloud dashboards, the mobile app, Alexa/Google Home support, and integration with cloud-only services, any of those would be a good guess--not a great guess since all of them currently work as-is and many of them have been around since the beginning and I doubt they'd backtrack and charge for things they didn't charge for before, but all we can do is guess at this point.)
Staff have also stated in the past that they have ideas for the future of the organization that they will not share publicly. in any case, I'm happy they seem to be doing well so far and I certainly hope they continue to do so in the future! I'd gladly pay a reasonable subscription fee for access to "premium" cloud (?) services or even just their amazing, responsive support.
In the event they do totally fail, unless they open up that is currently closed, the truth is that it's not 100% local. It still requires a cloud connection to download the initial firmware (unless something has changed recently) as well as updates (not like you can just download a firmware file from somewhere and upload it to the hub yourself), so even if you already have a perfectly functional hub, it will be a tricky situation if it dies, even if you have a spare (less so if it's already loaded with firmware, though). Obviously the cloud would stop working, so cloud integrations like the Alexa skill (the app might work...) or any of the native or community SmartThings integrations would stop working. If this happens--and I obviously hope it doesn't--I think I'll continue to use it as long as I can, eventually probably just becoming a Zigbee and maybe Z-Wave radio for Home Assistant (via MQTT, as I did when I transitioned to it from ST and Home Assistant in the first place) until I find something to replace the Z-Wave and (especially--this is something Hubitat excels at) Zigbee portion.
But again, hopefully nothing to worry about. 
