Google will be more than happy to let them walk away and allow remixes and user posted content to fill that hole (it's how YouTube started). VEVO will just come crawling back.
YouTube has a monopoly on online video and they may just turn out to be one of Google's most valuable acquisitions (along with DoubleClick/Android).
> Morris: If Justin Bieber and Adele are somewhere else, that will be where people will go. If you don't have the content, no one will come
YouTube has the people now (daily standing subscriber audience + network effects) - the content comes to YouTube not the other way around. People pay/share video revenue on YouTube by posting via Machinma/IGN just to get exposure.