WWTBAM was part of Meredith's contract with ABC to keep her on the View a few years ago. Considering potential replacements...
Well, there's an issue of Regis potentially competing with himself (eg, Regis & Kelly), so they won't put him on both shows at once. That would limit what stations can have WWTBAM and that would be very bad in the long run.
I agree with the sentiment that Bergeron is a very good choice for a replacement. He's done this type of show before (Squares), and we know his ability to have fun with the contestants is pretty good.
Another good choice would be Vicki Lawrence. I think she'd be a very good choice for this show, she's got the personality and she DOES have the experience in hosting a game show. Plus she's well known, which helps her considerably.
One other choice that might work is Howard Stern's sidekick Robin Quivers. She's got a great personality, she's played the game, she can relate to ordinary people (well, think of it this way, she has deal with Howard's guests every day!), and she would be the first black female game show host. (It also doesn't hurt that she's in NYC and could easily do Millionaire in the afternoons...at one point they were talking about giving her a talk show in syndication anyway)
Jane Pauley might be an interesting choice, but considering how she flopped as a talk show host, I'm not sure they'd want to put her back into syndication again.
As it was discussed a few years ago, they had a very tough time finding Meredith, and finding someone to fill her shoes will be even tougher. (and since Dick Clark's not an option this time...there will be a long search for a host.)