The #8 can't be sold but there is still a slight possibility.
http://msn.foxsports.com/nascar/story/6960276
A quote from Larry McReynolds
"If Dale Earnhardt Inc. makes a run at Busch, it would make sense DEI and Hendrick to swap the No. 8 and No. 5. Rick Hendrick may be the guy to negotiate that deal with Teresa Earnhardt,
but I believe that she would do anything on earth to keep Earnhardt Jr. from having that No. 8, just because"
Even if Nascar allows them to swap she might not want to.