Off topic but a reply to this. It's all about money, market share, competition etc. It seems that MS and Sony actually talk about X platform gaming. True or hoax? You/we can imagine multiple reasons why MS reaches out to Sony right now. See it from different angles and different ways of interest. At the end it all has to do with money.
https://www.gamespot.com/articles/microsoft-confirms-its-talking-to-sony-about-cross/1100-6452820/
So to add to the question of @CSLACR : SMS would love X platform for PCars2 for sure but then it also needs X platform compatability from the hardware vendors and also the online servers need to support interoperability. Long way to go or never going to happen? Time will tell.
From a technology point of view it is already possible. But then we also have to deal with sales and marketing
Some games seem to pull it off.
And tbh the forst game that has x platform compability surely will draw the online crowd, will probably 'win' the e-sports crowd over (big money in there). And therefor be the biggest racing game.
This is all speculation. Stupid profits will once again delay the progress of society (however insignificant this is) ==> and this is why kapitalism as we know it will be the downfall of the human race.