I'm sure they would just add another tier of weapon instead of just adding +3/4 etc. I think it would also be nice if the different elements actually looked different, but I guess that might be a bit much to hope for...
They already added the +3 version in the test servers, but beyond that I agree that they will upgrade the staffs to a new one, possibly the elements having their own unique look (maybe separating element groups apart as well, but highly doubt it).