I don't think it's going anywhere, considering that I'm very sure Pikes Peak is coming in the next game. I think PD even scanned a Peugeot 208 that was outfitted for it. And I don't mind it sticking around, either, especially if they have more time attack stuff like the Goodwood Hillclimb, or that frankly neat GT5 rally mode, where the courses had some randomization to it, and you even had a co-driver.
I'd love to see the Gr.B group expanded, too, especially since some famous rally manufacturers that seem like a shoe-in are unusually absent, like Lancia and Peugeot. Some other automakers could also debut in Gr.B, like Daihatsu or Porsche. Maybe there could even be a Gr.C for older rally cars from the '70s, like the older Lancer and the Stratos. Either way, I bet the Escudo could fit into Gr.B, somehow, and I think it could be telling that the only real-world rally car in Gr.B is a Pikes Peak car.
I think off-roading is inseparable from GT, for better and worse, but I do look forward to what's next, especially with Michelin's help with the tire modeling, and the possibility of Pikes Peak content coming. I'd also love to see if we get a time attack mode around the Isle of Man course, given the rumors that PD was scanning it, and they added that Isle of Man-spec WRX STI to GT Sport. I don't know if I could imagine racing cars on the Isle of Man, but could certainly see it as a possible successor to the Circuito de la Sierra Time Rally from GT6.