I rly hope that Blizzard makes an co-op campaign... (Now, if I werent noob at creating threads I would have a poll but I cant....-.-) Do you want Blizzard to release the game later, but with co-op campaign?
Uh... when you make a new thread, there is an option, I think it is a checkbox, that says "Do you want to post a poll with this topic?" or something like that. To answer your question, yes and no. I would like Blizzard to release a co-op feature in the campaign, but not take any longer. I'm not a programmer but I think that turning a single player map into a two player map isn't that hard.
IIRC: When they were asked if they were going to do [insert gameplay mechanic] similiar to Dawn Of War 2 and they gave a cop-out answer of, "That's an interesting idea but it doesn't work in our circumstance" or something similiar and they mentioned that the single-player campaign would be, just that, single-player. Could have been something else though and I wouldn't be surprised if they had some co-op side missions. I'll try to find the article. It was on IGN, I know that. Now, that we're on that subject. I'd rather have co-op side missions than co-op core missions since that could throw-off the story and gameplay.
It should be easy enough to do for mappers so hopefully will be an option and we'll see some nice coop fan campaigns.