I would argue that it is already in the top Four. Hockey had its brief chance in the early 90’s, but it went nowhere. Hockey is pretty irrelevant nationally in the sports conversation. Even in Canada, the sport on the grassroots level has become a sport of the well to do. It is so expensive to play, that a large percentage of NHL draft picks today come from the upper middle class or wealthier. In the next 15 years, I predict soccer will be in the Top Three, passing baseball. Baseball’s over 55 nursing home fan base is not healthy for MLB’s long term prospects, plus on the grassroots the sport has collapsed. In my area, towns that fielded 10 teams on the LL level are having trouble fielding even one team today. I say this with no pleasure, as someone who played baseball at a high level.
Or from Russia, Sweden or Finland.
Which is kind of the point that “American” sports aren’t so American anymore.
Baseball is full of players from Asia and Latin America.
More NBA players come from Europe and South America
NHL players from Russia, Finland and Sweden (not to mention Canada)
That pretty much leaves the NFL.