Check my edit. It says UPLOAD. So yes, we will be able to upload.
And if they make it so that we can upload it straight to Youtube, they would not need to use their own servers. The conversion is made by the console you're playing with, and uploading is being made by your connection.
Just because Halo doesn't include that, it doesn't mean it can't be done.
As for the bolded part. That makes no sense, sorry. Dunno how it works on the 360, but the PS3 has a few games that have upload-to-youtube system. One of the titles is Noby Noby Boy.. and do you know how much that game costs? Around $6.
So yeah, having the option to render the video and upload to youtube is not expensive. You just have to add the option to your game.