I think GT7 is a wildcard for this generation.
While Spiderman might enter 30+ Million territory with the PS5 remaster, God of War & Uncharted are around that 20+ Million tier, which is where I think GT7 can leg itself into. A spinoff GT is reportedly close to 10+ Million and that's with poor critical reception in comparison to GT franchise standards. Considering this is a full fledged GT coming early in the PS5's lifecycle, the fact Sony dominates in GT's most popular region, the unique features of the Dualsense and how it intertwines with the racing genre, and the franchise traditional evergreen sales, it might be the perfect storm for GT7 to reach 20+ Million sales.
I would love a GT coming back to life, it was able to sell 10M ever since PS1 and reach almost 15M in one entry (and GT5 if you pick also prologue sales passed 15M), if they series experience a growth similar to the other studios then GT could reach 20M (I think it is unlikely, but who knows).
Probably a dumb question, but when a game is free on ps plus do those downloads count towards sales of the game?
Nope, they count sales not downloads. If they counted downloads UC4 would probably be over 50M as it was also gave away in PS+, and most of the exclusives weren't gave away in PS+.