I loved this movie. I did not feel it was unnecessary since I wanted to know what would happen to the toys after Andy went to college. It makes some sense that Bonnie would become the new main kid to play with these toys since Andy passed them off to her. I liked the questions that were asked in this movie because to me, it made the toys more relatable to people, having them deal with real-life problems.
I understand that some people felt like this movie was a cash grab since they thought that Toy Story 3 was a good ending. I can see their point with that argument but I can also see why they made the movie- to answer the most important question: What would happen to Woody and the gang after Andy went to college?
My theatre really enjoyed the movie.
I felt like the movie answered that question enough for me to be satisfied. I suggest seeing this movie, if not to end the series, to listen to different perspectives on the subject of change throughout life. Make sure to stay for scenes after the movie.