When I was at EA, Madden & the NBA game were in pretty sharp decline. Offset by FIFA’s incredible growth. So this already happened, at least once anyway. How those games are doing these days I cant say.
But as @Navaronegun mentioned there was a lower limit. For some core sports fans the Playstation or Xbox is “The FIFA machine” or “The Madden machine”. While the audience for consoles is aging, there are probably more than enough core sports only players to sustain the business for some time.