I was curious as to what this implies, so I did some quick/superficial googling. The page in the OP has a Yes next to Intent To Use - this appears to mean they have a good faith intention to make commercial use of the trademark within the next 6 months. If for whatever reason they could not make use of it within that time, they can file extension requests indicating good cause for being unable to do so, for six months at a time, up to 5 times. So, OpenAI ostensibly intends to make available a commercial product named GPT5 within the next 6 months (or up to 36 if there are unforeseen delays). So, probably before mid-january.
I welcome corrections from people with actual knowledge, I just did some quick googling because I was curious and thought I might as well share what I found.
Their official statement was, that now the GPT versions will only improve in small steps, and no really big releases at a time. This would mean, that they only saved the trademark for later use, so that no one else gets it. But, while this was an official statement, OpenAI is still a company, so they might have made this statement just to appease their competitors.
My guess based on those statements is, that GPT-5 releases around mid of next year, but we'll see.
Don't you have to be using it? Or at least plan to in the near future? Or else people would just register trademarks for everything just to squat on them and sell them at a premium later on.