There was actually a pretty good article about the Denisova human in one of the recent National Geographics. One of the researchers mentioned in the article made a similar point, that for him the most likely indication of the Desnisova find is that we currently are separating into sub-species where there aren't any and that what we are finding are differences between individuals and not new sub-species.
I wonder when/if that will be the established view and some of these species will be consolidated.
