Comment by ilaksh

There may be conventions but in no way can anyone force them to follow them. It's just a name for a release. They absolutely are working on the successor models and have stated they plan to release a model by June. Whether they are working on a new architecture or training running, they certainly have experiments, but who knows how serious they are.

Regardless they can and will call future models anything they want. They could easily just decide that the minor improvements that come out in a few months are called GPT-4.2 and the major new training run is called GPT-4.5 instead of GPT-5.