There's no broken promise though. It's the users who decide+assume, on their own going in, that X project is good for their needs and they'll have access to future versions in a way they're comfortable with. The developers just go along with the decision+assumption, and may choose to break it at any point. They'd only be assholes if they'd explicitly promised the project would unconditionally remain Y for perpetuity, which is a bs promise nobody should listen to, cuz life.