I don't think there's really any trends to the Hikago fandom just yet. I think the most you can say is that fanfic authors seem to be getting more adventurous in the fanodm: more willing to write AUs and take the characters in directions not explicitly stated in the series. This could just be authors maturing in their writing and handle of the series though. I'm not sure.

It's not like Hikago is like FMA or Death note for example, there's no new canon for fans to play with or grow with as the series progress. I guess since the series wasn't instantly popular when it was fansubbed, we don't have as much of a fandom growing with the series as other fandoms can boast.

/end stupid rant