So... are these legit?
From The Lost Media Wiki
Just found this listing for an early Toy Story 4 script on Hollywood script site ScriptCity. According to the site, this was written in late May of 2013, which would place it about a year before the official announcement. Only fishy part is that it's credited to prolific Hollywood writer Ben Karlin, although it's totally possible Pixar just payed him to pen out their ideas and thus he gets no credit in the final film, as is commen in the movie industry
Link: https://www.scriptcity.com/all-scripts/movie-scripts/toy-story-4-detail