Davison's been my bet all along as well, well known and succesful but not so succesful that he wouldn't be up for it, plus he fits into the 'older star' category that Strictly always have at least one of. Of course there are those rumours that they were trying to get Jenna to do it as well.
As a dark horse I'll throw another name into the ring; Louise Jameson. In terms of classic companions who are still with us she'd be quite well known given her output (Who, Bergerac, Tenko, Eastenders) plus she still looks good even though shes in her 60s.
People unlikely to do Strictly;
Colin Baker (although frankly Strictly would be better for his health than I'm a Celeb likely was)
Tennant, although that'd be a hell of a coup!