I hope you can get he crossbows without joining the Dawnguard I am sure you you would be able to. It would be a shame if the crossbows were restricted to the Dawnguard, and that would limit your choices when expansion are supposedly supposed to expand your choice so you can have the freedom to do what you wish in an ES game.

Another thing I am wondering is how many crossbow types there will be. I hope there us several of them not just two types like Morrowind. I want variety for my characters.

Another thing I am thinking about is since you can craft bolts what about arrows, now there is a thought since they are expanding their crafting system.

I agree, arrows should be craftable as well. I also think arrows/bolts should be put in a new Ammo tab rather than the cluttering the weapon tab.

I would be sincerely disappointed if crossbows were Dawnguard-only.