Like you mentioned yourself, now FM6 has PCARS, FM5 (which wasn't released that long ago) and Forza Horizon which take a part away from the Xbone segment. On Playstation i suppose Driveclub sold very well and there was no 'next gen' GT yet so i don't think we need to worry at all. People still like a driving game on their consoles just like they did 10 or 20 years ago, there's just more of them and they are better in quality.PCars and Forza are probably seeing themselves in their mirrors, PCars investors return (and lack of PR) doesn't seem to place it above 2mi. PCars sold ~150k PC, ~250k X1, and ~600k, in its first full month. 7 months later PC is at 330k after being heavily discounted (AC is at ~300k), and it basically didn't chart in Europe the whole year (passed 100k PS4 in Germany in October, Sony's now largest market in EU).
And there's of course Shuhei Yoshida's statement about the "driving genre being hard" at this moment.
Don't think it's decent competition driving everyone down.