In Morrowind, you could become a Werewolf. In Oblivion, you could become a Vampire. Do you think they'll include both in Skyrim? I was very discouraged from being a Vampire in Oblivion simply because if you didn't feed every day you couldn't go out in the sunlight. Although I highly doubt this, do you think they'll make some vampire / werewolf mix?
Time to educate you. The book, http://www.imperial-library.info/content/daggerfall-on-lycanthropy, is the best and only source we have about were-creatures. Also, you could become a vampire in Morrowind, one of three types no less.
As for Skyrim, we know of a type of vampire that moves through ice and snow in Eastern Skyrim (where it is the most cold)
He wanted to know about the vampires of eastern Skyrim. I told him about the most powerful tribe, the Volkihar, paranoid and cruel, whose very breath could freeze their victims' blood in the veins. I explained to him how they lived beneath the ice of remote and haunted lakes, never venturing into the world of men except to feed...
True to his word, the man returned to my chapel shortly after midnight four days later. There was a fresh scar on his cheek, but he was smiling that grim but satisfied smile of his.
"Your advice helped me very much," he said. "But you should know that the Volkihar have an additional ability you didn't mention. They can reach through the ice of their lakes without breaking it. It was quite a nasty surprise, being grabbed from below without any warning."
As for were-creatures, the two known types in Skyrim will be werewolves (as they're supposed to be everywhere) and werebears (native to Skyrim and supposedly the lycan with the largest population).
Also, vampires cannot be out in the sun, that is established. The only reason the Cyrodiil clan could was because of a deal they made with C. Vile. Everyone else is stuck as nighttime dwellers, but they don't need to feed all the time.
Oh and it's impossible to be both a vampire and a were-creature, as both gain disease immunity upon infection (save for mods and glitches, you dirty cheaters).
And no lycans vs. vampire crap. Vampires may be able to continue to think, but lycans are much different. They are the hounds of the hunter, Hircine. The curse was crafted so that the afflicted would be consumed with an all hungry bloodlust, whose only purpose is to hunt. Hell, if lycan saw another one, the two would likely try to kill each other. The only time lycans will come together and work with each other is when the hunter himself makes his presence (like in BM)