I don't think the game could use a fourth Wolf...I think they were counting the Arctic wolf as one of the subspecies of Gray Wolf. The only two traditional wolves we have in the game that I know of are the Timber Wolf and the Arctic Wolf and they did say two subspecies. So I think they just forgot or didn't know about the dingo being a subspecies of wolf because then that would make 3 subspecies.
Personally I'd prefer Red Wolf or Ethiopian Wolf if we get another wolf though because they are different wolf species and not just a subspecies even though I do love the look of Mexican Gray Wolves myself but think that's more of a it can be covered by mods than it should be an official animal status since all the behaviors and vocalizations and habitat needs would be the same as the Timber Wolf anyway and only really the look would be different.