The trouble is, being rich already is a sustainable business model. If you have a tool where the only developer(s) working on it have made enough money that they don't need to continue running it commercially and have no personal interest in building more than they already have, paid upgrades are no guarantee of anything from a user's point of view.

As a counterpoint, as long as the version you already have is useful, and as long as it's a permanent copy that is not going to just stop working if the supplier takes their ball and goes home (I'm looking at you, Adobe), all you're risking is not having improvements that you were never guaranteed anyway. If the current version is better for you than whatever else you could have used instead, it's probably still worth buying it even with no future-proofing, IMHO.

In fairness, for tools you use everyday, you want constant upgrades if only so you can use it on newer hardware when your old rig dies.

As ST2 will continue to run forever without a purchased license, I doubt anyone is rich.