I don't think it affects sales. The XBO has been having it's best year sales wise and the Switch is selling really goof and they both have crossplay.
Mentioning that MS has a pay wall for F2P is like a kid getting in trouble and then being like "but so and so also dI'd this", doesn't make Sony's problem any better.
Personally I'd love to see crossplay become the norm with PS4. For the last few weeks I've been playing with my friends that game on PC on Fortnite and RL. Also gonna start playing RL and Fortnite with my sister today. Will let her use my Switch and I'll play on my Xbox.