Woody will wear a special holiday vest decorated with a Christmas tree and presents, plus a candy cane stuck in his holster. Jessie gets a special vest as well with a peppermint pattern. Buzz Lightyear will be wearing a sparkly Santa hat.
The entire new land will be decorated as well, with oversized cranberry-and-popcorn garland, a huge Hamm sugar cookie, Green Alien ornaments, and a giant holiday card featuring a selfie of the Toy Story pals.
Source: Disney Parks Blog