Actors on talk shows aren't always the most reliable sources for production news, especially when it comes to huge franchise films. That's not to say that actors are innately untrustworthy, it's just that, unless they're also a producer, they tend to only ever be involved with a small slice of the production process. So even though their agent may have told them about Thing A at one point, it can turn into Thing Z without them ever knowing about Things B through Y.
He outed the previously unannounced film on a BBC talk show this morning (which makes this our third unexpected Tom Hanks post to have emerged from the Larry Crowne press tour). It was actually a rather understated announcement for what would definitely be a huge deal for Disney/Pixar. One of the show hosts asked if there would be a fourth film in the franchise, to which Hanks simply replied "I think there will be, yeah. Yeah, yeah, they're working on it now. There you go."
And while this post did begin with a warning that actors on talk shows are unreliable sources, Tom Hanks is so intrinsically tied to the Toy Story franchise that if any actor were to know of the existence of Toy Story 4, it would be him The question of course is, what would the movie even be about? Toy Story 3 wrapped the franchise up in such a beautiful bow that we don't know how Pixar could possibly top it. Frankly, we're not even sure we want to see them try.