If PD wants to add Formula E, some of the city courses from that series could come to GT7, too. They also could end up replacing the various GT4 city circuits, as I'm pretty sure Formula E has had races in the likes of Hong Kong and NYC. (Though GT4's NYC circuit was in Manhattan while Formula E's circuit was in Brooklyn.)
Either way, I get this idea that PD would avoid having too many courses based in the same nation/area, so I could see Phillip Island or Watkins Glen being added, in that regard. (With Daytona being in the southeast, Laguna Seca and Willow Springs being in the southwest, and Watkins Glen being in the northeast.) I think we could potentially use more German courses, too, as well as Italian and French circuits. Idk, maybe Imola or Mugello?
But at the least, I really want all the real circuits from the PS3 era to return, including the Goodwood Hillclimb (which could appear alongside the circuit), Silverstone, and Ascari, alongside the 80's versions of Brands Hatch and Monza.
I also think it's likely we'll see some entirely original circuits set in real locales again, following in the vein of GTS and courses like St. Croix and Dragon Trail, versus previous original circuits where the real-world location was much more vague. Compare Special Stage Route 5 to Tokyo Expressway, or Trial Mountain to Alsace - though Trial Mountain is now confirmed to be set in the Sierra mountains of the USA. I think there were only a few exceptions in the pre-GTS games, like El Capitan. Though I'm purposely excluding the PS1/PS2/PS3-era city courses, as they were set alongside real roads.