I highly doubt we will see another Unfinished Business edition this soon after the last one. I have my doubts about them doing an All Star edition any time soon either. As for Brenchel, they've taken people from Big Brother before, so why not?
I saw Russell Hantz tweeting lately with someone about being his partner on the Amazing Race, but he was on Twitter yesterday. However, given his history of leaking info about Survivor and since teams are probably already sequestered, I doubt he will be in TAR 20.