I have a hard time seeing Driveclub "back at the drawing board". That game was pretty much done so if there's any game I would rush out just to get a driving game on PS4 it would be Driveclub.
PD are most probably working on GT7, but I don't think it's related to Driveclub.
Here are the version updates of GT5 (blue) and GT6 (red) during the first 112 days. The update pace so far looks pretty consistent with what happened during GT5, so it looks like it's simply the pace by which PD is producing content post-launch.
View attachment 133348
It took 87 days before 1.05 was released for GT5. By that time the total update size was 1383MB.
It took 95 days before 1.05 was released for GT6. By that time the total update size was 2813MB.