They don't have the characters to do it, neither do Sony. I don't think the realistic characters like Master Chief, Marcus Fenix, Kratos or Nathan Drake work. Even though Snake was in Brawl.
Predictions (Made July 2019)
LTD: PS4 - 130m, Switch - 110m, XBO - 52m 2019 : PS4 - 15m, Switch - 18.8m, XBO - 4.8m 2020: Switch - 22m (Peak Year)