A few sites are currently reporting that Col Needham, IMDb founder and managing director, has said there will indeed be such a category. For example, Casey McKinnon is reporting exactly that from this year's SXSW fest:
Online Video Categories Coming to IMDb
"The answer is a resounding yes. In the second or third quarter of this year (anytime between April 1st and September 30th), IMDb will roll out the ability to tag a submission as either a web series or an individual (one-off) online video."I've listened to her audio of the question, though, and it sounds to me as if he says they are "toying with the idea."
I wasn't there, however, and she seems certain -- even presenting that timeline. I do think they'll have to address it, of course -- and I'll be very happy to see it happen. I've got a lot of credits for online work that would be added.
Another discussion of the big picture, written by David Nett, is well worth a read:
IMDB and Web Television
We'll see how this one works out.