Where was it said Japanese will be more popular?
That's how I understood Learning Japanese will be usual in the next few decades. Anyway the general point is to be committed to that cursus is, I agree with you. Doing it because of videogames is not a less viable motivation to do it, however to be blunt I have heard of many a story of Japanese classes being overpopulated by people being infatuated by that specific segment of culture but ultimately not being that motivated to really follow through up to the level of proficiency needed to either get a job with it or living over there.
Anyway... Mauricio permed 
The problem is that people think every anime or game fan isn't in it for the language and culture and history too.
I might love manga and games. Those are the main reasons I did it. But I also am interested in the history and culture too. A lot of game and anime fans that learn it because they're otaku rarely stick with it and ultimately think that it is the only thing that represents that country. I don't like otaku as much as anyone else. But liking manga or games doesn't make you an otaku by itself.
But yes, you're right. A lot of Japanese classes are full of otaku nerds and they're disgusting. But that doesn't make wanting to learn due to games as actually invalid reason because. People like Bebpo who are good at the language learned it for the same reason. The problem are the people who think Japan is Akihabara only and don't give a fuck about the history of Osaka or Eihei-ji. I know I'm an outlier. Even moving to the country won't solve things. I hear lots of stories of people working in Japan, only going to places like akihabra, only hanging around foreigners, not putting any effort into learning even though they're there. So even then it's not a cure all. I think it ultimately comes down to effort, which is no different from any other aspiring language learner.