In that case more non-japanophile niche boards may be a good idea, to encourage discussions that isn't japanophile bather. So that those dicussions won't be lost amongst the more otaku/japanophile style general babble. Judging from my mom, having a bunch of kids babbling about random general silly things would be a turnoff for her, and it would make her feel at east to at first spend time at a board more fit for her and her likes before she would feel like mingling with the general "riffraff". I probably should mention that my mom annoys me sometimes. She's an intelligent woman, and interesting. But being her kid is not too good sometimes. (mom dragged into discussion since i was assuming 4ch was trying to attract people of all sorts, and not just young teenagers. Not that i'm a teenager anymore but that's beside the point)

Create, and they will come. Provide good enough atmosphere and they will return. The latter however being a responsebility for all of the visitors at a board and something mods and similar only can encourage.
The reason for why i've never bothered visiting world4chan is mainly because i never ever actually noticed it.
I've been visting 4chan for a year by now, but it's pretty much mainly two boards i visit, and once in a blue moon wander off to the other image boards. Since i virtually never surf with the frame on, world4chan is an easily ignorable, cryptical link on the other side of the top. Had i know, i definitely would have visited it though. C'est la vie.