Sorry, yes you're absolutely right and I'm being unclear. I'm a reasonable programmer but not a good writer.
When I say "rename" I don't mean going from "Snow Leopard" to "El Capitan". That's stupid, yes. (And it's also marketing, which I know even less about. So I have no comment on what an improvement would be.) My proposal is going from "Rails-4" to "Rails-5". Which would have the same benefits as 10.11 and 10.12.
The comments I've gotten so far are making clear that I failed to set the stage for this post. The scenario I'm concerned about (as are the links I refer to) is this: you have an app you built, and it relies on some versions of other libraries. You'd like to periodically pick up bugfixes and security fixes for those libraries without it turning into a bottomless time-sink (because your libraries failed to adequately distinguish between compatible and incompatible changes). How do we do that? (It's not just about tool design, it's about eco-system design.)