I don't think you have to worry there. In regards to Pokemon...let's take the Roleplay forum for example. I can't remember the last time I was in a Pokemon roleplay. It must have been at least a year, but I've taken part in a number of other RPs since then. My point is, despite this being Pokecommunity, there is a lot of non-Pokemon content that people actively create and look for, so I don't think that your writing will generate any less interest because of it.
And as for MLP and furry stories, do you really think that people wouldn't be interested in that? There are quite a few MLP fans on the site, so I don't think you'd have to worry.