This market resolves the same way as this market: https://kalshi.com/markets/gpt5/gpt5-creation

"(…) OpenAI has announced the creation of a new large language model named GPT-5. A large language model by another name (such as GPT-4.9999), or which is referred to as a spiritual successor of GPT-4, would not fulfill the Payout Criterion."

As I read it, that market isn't about whether GPT-5 will be released by the end of the year, but about whether OpenAI will announce the creation of GPT-5 by then.