[Marsh.]

Yeah, to make a proper announcement Channel 5 will want to give immediate details to get people attracted. The presenters fixed, the format, when it starts etc.
Rather than announce that they've agreed to bring it back, they only want to announce it once deals are signed and things are 100% going ahead.
So, they probably contacted Davina to give her first chance at presenting it before offering someone else and then she's given them the go ahead to look for someone else (probably Emma Willis, who she's already put forward as an option).

But I don't blame Davina really. The whole ending last year and Davina's Big Send Off and when it was showing their final days in the studios celebrating the end of it all would seem a bit silly to just pick up a year later as though nothing happened.

If they asked her and told her it would be back on another channel this time last year or just before BB11 started she'd have probably jumped at the chance to carry on but it would be silly to do it now.