Regarding the spork thing, maybe the theme is that fun "toys" don't always have to be bought from the store but can be made yourself. I think that would be a cool concept, but really confusing how Disney would end up marketing that if the spork turned out to be a main character! Edit: I just read up on it some more and I'm actually pretty close, lol.
Original plot outlines had this as a "prequel" focusing on Woody and Bo Peep's romance but that seems to have changed. Latest IMDB plot outline says “Woody has always been confident about his place in the world and that his priority is taking care of his kid, whether that’s Andy or Bonnie. But when Bonnie adds a reluctant new toy called “Forky” to her room, a road trip adventure alongside old and new friends will show Woody how big the world can be for a toy. Along the way, Woody is reunited with an unexpected old friend.”
All I have heard (no spoilers) is BRING TISSUES because this is going to be worse (in terms of a cry factor) than TS3.