They certainly are a fad. Hard to say if demand will be there in the future but I don't see why not.
More money could be made owning/stocking the novelty machines that sell these though (since it is difficult to complete a set because the next figure purchased is always random).
In Japan, novelty machines can charge upwards of $3-5 for random toy figures. The craftsmanship is there but it seems like a lot for a random throw. Many of them are even aimed at older buyers (they aren't toys really).
Even the homies have been written up in magazines for older people.