I read it on a disney instagram account, I assumed that it was an official statement since they were instagramming live from the
D23 expo, but I'm not 100% sure. Here is what they posted:
"The reimagining of Disney's Hollywood Studios will take guests to infinity and beyond, allowing them to step into the worlds of their favorite films,
starting with the all-new 11-acre Toy Story Land. Guests will become part of the adventurous outdoors of Andy's backyard, including two new Disney Parks attractions and one expanded favorite."
That line led me to believe that Toy Story was just the beginning of the Pixar expansion. Although now that I think about it, the statement might mean that they will start construction on Toy Story Land first, and finish Star Wars land later. Still, I would hope that Toy Story wouldn't be the end of the Pixar attractions added to the park.
if you're interested, @lotso_at_disneyland is the instagram account I read this exact statement from.