GRR has seriously recommended to HBO that they could just do prequel seasons until he catches up and writes the books. LOL. They nixed the hell outta that shit. Seasons will come one a year.
Here's the truth, the show has already lapped GRR, or very soon will. The actual scripts are written almost a year before shooting even starts. Why? Because of practical reasons, of the mamoth task of budgeting and tasking. For logistical reasons the scripts are already written.
The fifth season is about to premiere? The 6th season is already written, and the 7th one is probably being worked on already. Depending on how long the show goes for, which the creators have said is 7 perhaps 8 seasons. They may be writing the end of this show next year, and are probably already thinking about how it ends, in a very concrete manner.
GRR on the other hand, might take another ten years to finish the series, realistically speaking. GRR HATES, absolutely hates writing them. He makes it sound like its a death sentence, and he would obviously rather be interacting with fans, giving interviews, asking his fans to bring him food.
The show lapping him, is probably going to be very embarrassing for him, but also helpful, because he can just use that as a template to finish them off, otherwise god knows when it would've come.