The Crystal Palace will be closed for refurbishment from January 3 - February 15, 2010. During this time, there will be characters added back to the Liberty Tree Tavern at the Magic Kingdom. Unfortunately this will be Minnie, Chip & Dale, not the Pooh characters.
While there will not be an opportunity to dine with Pooh during your visit, you should have no problem meeting him. Pooh often greets guests in other locations in the parks. He is often at the Animal Kingdom, and I suspect that they may add a Pooh greeting near the Pooh ride during the Crystal Palace renovations.
To make sure that you're not missing Pooh and his pals, I would go to the Guest Relations office at any of the theme parks;
these are noted on the park maps. Ask them to call the "character
hotline" for you. The character hotline will be able to tell you if
any particular character will be in the parks on a particular day, and
if so, exactly where and when the character will be there.
Enjoy your visit to Walt Disney World.