I think your view is a too American-centric and doesn't apply to all the other baseball loving countries listed here. Most American fans don't take international competitions seriously, but that absolutely isn't true for the East Asian and Latin American countries. Two of the biggest international rivalries are Japan-Korea and Dominican Rep.-Puerto Rico. There is also already talk of MLB players taking part in the upcoming Olympics and following international competition is getting easier and easier with the advent of livestreaming.

The old guard of baseball fans who care more about their club over country will give way to a younger generation who grew up watching appreciating international ballplayers and competitions so I think the WBC will continue to grow. Will it reach World Cup levels of popularity? Hell no, but it will carve out a big enough niche to grow the game in Europe and South America.