Any model which is clearly the next major, canonical form of GPT will count for this market regardless of what it is called. I am assuming this will be called GPT-4.5 or GPT-5, but it still counts if it has another name. A larger context window does not count, a jump like GPT-3 to GPT-3.5 does count.
All options resolve NO as that month arrives, until when the next model is broadly released and all remaining options resolve YES.
Related questions
All of these markets in this comment should be arbable, as I believe they count either 4.5 or 5.
Beware of the various other markets, which have criteria requiring it to be specifically named one or the other.
@Joshua Thanks for posting all of these. In addition to these 243 markets, I've identified an additional 82 that may be arbable.