This concerns me as well. I have three Dolphin licenses and Dolphin and unless I'm wrong, Dolphin will work for another year or so until Flash is finished. maybe it will continue to work after that, but I'm not very good at reading foggy crystal balls. As @Travelnotes has mentioned here or elsewhere, Dolphin is old technology with a tired interface and big changes are needed for Cheetah, or any other fork for that matter to be successful.
Facebook has killed the social networking market and fewer people are brave enough to start their own sites. I have a niche clientelle, but the word is, "We like Facebook even though we have to hunt for the things we want." One of my niche sites has a miserable 60 members, whereas there are over 200 similar groups scattered over facebook. I liken it to Australia's worst Telco, with a shocking track record for quality and service, yet 80% of the population use them. The shop next door offers cheaper prices and a better service, but it's empty. The market leader has people queuing past the empty shop waiting to be served.
Because most people have adapted to mobile phones, few today are interested in creating or programming a site of their own. If they do, they're looking for a "Wix" solution of plug 'n' play. Sadly Dolphin/Cheetah is a far cry from that style of programming. In the early days when I became interested in Dolphin after building several non-internet databases for point of sale and costing, I concluded that most new Dolphin users abandoned the script within days, if not hours. I gave up because I was getting nowhere and became interested in Elgg because I was able to purchase a book that showed me how to use the script properly. I loved Elgg, but my users wanted a forum which Elgg didn't have. I then moved over to Oxwall which I also considered superior to Dolphin, but it never had the likes of Anton and Modzzz backing it with great third party modules. I also wanted a three column Gui, but Oxwall only supported two, something I appreciate now.
Finally there was Wiccle, but I arrived just as they slammed the door. They had a good concept; a free version with limited modules and a commercial version with most bells and whistles. Wiccle had a lot going for it and I'd love to see a few features end up in Cheetah. Sadly my free version of Wiccle which I still have, needed a free key to continue operating after 30 days. They closed down before I had a chance to get that key. If anyone want's a copy of the script, I'm happy to send it to you. I'm not sure if it will run on PHP 7.2 though. It's no good for a production site, but it has some great ideas.
So where does this lead us? Well I'm also concerned that the the demand isn't there for Cheetah to be financially viable, thus I was hoping to see it become a community project. I'm not able to contribute with coding, so my view isn't biased. I just feel it has a better chance of survival in the long term. Deano could still make money by offering $5-$10 tweaks. (I'm using that amount as a suggestion because it's proven that people don't mind spending five or ten bucks, but stop and think hard if it's any more. The tweaks don't have to be modules, but simple hacks that make the program better. They could even be built around an override system used in ZenCart or the template system in Cheetah.
I guess I'm suggesting that Cheetah first becomes stable and free with maybe a few small additions. From then on, I'd be happy to see Deano make those "affordable" hacks or even develop modules. There seem to be a few individuals out there making some kind of living from web programming and I've often mentioned Pablo from WYSIWYG Web Builder. He charges around $US 50 for new users and $30 for regulars to supply a version filled with dozens of new features. I started at version 4 but now its up to version 15 and I've purchased most in between. https://www.wysiwygwebbuilder.com/ It comes with hundreds of templates and extensions, so it does represent great value for the dollar. Cheetah must do the same to gain a market share.