There's no information on this yet, like others have said. I don't believe theres going to be uploading straight to Youtube, but it has been confirmed that you can upload to their website, which I'm guessing you can go on the website with your pc and rip the video. From there on you can further edit the video with whatever you like.
My only problem is that the replay system, is it really going to be precise? Look at Crossfire for example (a free MMOFPS by z8games). They have a replay system, which saves the button presses and mouse movements, and emulates those in a "video". It isn't accurate at all as you can see that when you scope in with a sniper, its way off, often times that look like yards off. If Black Ops replay is like Crossfire, I don't think it is going to be all that amazing. Then again, if that one reveal was REALLY made in the editor, then we have nothing to worry about, and it CAN be uploaded to Youtube.