just a quick question. Is there any word on this?
if not i think it would be cool for the Dark Brotherhood to help you in your quest to defeat the dragons attacking Skyrim

Like Fallout : New Vegas where you recruit sub-factions to help you in the battle of hoover dam?
I could see that. Well, as long as it was a battle near the end and some guilds wouldn't help because another is participating etc.
Or are you talking about simple dragon hunting in the wilderness? but getting aid there just spoils the whole 'dragons are boss enemies'.

Nothing official, seeing as we can only have one companion at a time if they do help it would only be for major battles.

it would be good none the less