Davina herself said that if Channel 5 had accepted the rights to BB earlier than they did and offered her her job again, she would have strongly considered it, although she did say that she spent a year preparing herself to say goodbye to the show when the announcement of BB's cancellation on C4 was made in BB10.
I'd love to see her on BBBOTS. She did see last summer's CBB, based on the tweets I saw (and plus Julian Clary's a friend of hers), so I think she'd make some useful contribution to the panel.
Yeah, she said she'd turned it down because Channel 4 already gave her a big send off at the end of the show and she didn't want to come back because she had already said her goodbyes and had a good cry about it. Plus she said that she wanted to spend more time with her family, and she was unable to do that as BB took over her summer.