Resolves NO if GPT-4.5 or GPT-5 (or similar) is released.

Resolves YES if a more capable successor is released with a different naming scheme. Does not resolve if "GPT-4 Turbo" is released (not a successor).

Doesn't resolve yes if they "boil the frog" and just update GPT-4 continuously forever. 

A bit of ambiguity exists with the word "successor" in the sense that a sufficiently different agentic model might be released, but it has to be their most "general" model and beat GPT-4 in most respects other than cost or speed.