Story from AP/CNN
The official NBC release mentions Millionaire in passing but doesn't say whether or not she's quitting.

This Washington Post Article states Meredith will no longer be doing "Millionaire".

I was watching Meredith's press conference and when asked about her future on Millionaire, she said she wasn't sure if she would continue. She did not have discussions with Buena Vista yet. She said she loved doing the show, but she knows it would be hard to do both.

Yeah, right now I'd like a little more than the say-so of a Post writer before I take the "she's leaving Millionaire" angle as gospel.

And for their part, some NBC people have invoked Hugh Downs and "Concentration" and said that if she wants to keep doing it, it's OK with them. Neither of those people were Jeff Zucker or Bob Welch, however.

Jeff Zucker used the Hugh Downs line in the press conference. NBC will allow her to continue to do WWTBAM.