As Littlewing has pointed out, Werebears are confirmed to exist. The Author of "On Lycanthropy" was right on the accounts of the Werebeast he encountered and so I would count him as a credible source and say that all the Werebeast featured in the book exist. Just because they aren't featured in this game doesn't mean they don't. It would be unreasonable to expect everything we have ever heard of and speculated about Skyrim to be added but Werebears are a biggie. I still have hope for Werebears but it looks like Vampires will remain woefully stunted and innaccurate. I would also call the author of "Immortal Blood" a credible source. The Vampires seen in Skyrim are NOT the Volkihar we have known about all these years.
Of course they are. They're just seem different because.... um....
*forty minutes of awkward silence*
A DRAGON BREAK!