20-Year Prospect
As one of the four major sports that Americans (as well as people around the world) pump hundreds of millions of dollars into every year, we're fairly confident that baseball as a profession will be around for years to come.
Not in a weird, Interstellar-like, "why do we still do this" manner either, but as a real significant sport. With over seventy million people attending the games every year, they'll likely still need at least a couple stadiums to deal with the crowds (source).
Pro baseball has been expanding since the late 1800s, and that remains its goal (source). The farm system is proof enough that there are more than enough baseball players to fill dozens of rosters. Imagine if baseball creates another four or six or eight teams, in places as far flung as Mexico City or Montreal, Canada (again). That's a whole lot of summer balling in the near future.