So I was thinking about guilds again and it made me think back to Oblivion and the Imperial watch. I always wanted to join them and was disappointed when I realized you could not. I always loved their armor, and I think there would have been some really interesting quests if the imperial watch were a joinable group.
I was wondering if you guys think their will be a joinable guard/police guild in Skyrim.

I actually wonder that as well.
There is an Imperial Guard mod for Oblivion, however. It's just like most other guilds in the game, but much cooler.

that would be cool but i would want it to where the thieves guild and DB wouldnt take you on because of that.

There probably won't be. It's a cool idea, similar to the Imperial Legion in Morrowind, but I'm not sure if this will happen. I'd love it to, as I'm all for having a large variety of guilds.

Hopefully there will be both the Imperial Guard and some sort of rebel faction / freedom fighter faction in the game

Skyrim is apparently in the grip of civil war, so the possibility is there for the Imperials to be a loyalist faction seeking to quell dissent, and for the rebels to be looking to break free of the Empire. Could make for some interesting quest lines.

But they would need to be mutually exclusive. You'd have to join one or the other.

Yea true.