We had our time, let the next generation experience Toy Story
I think it's very selfish for us to say 'Toy Story 3 had the best ending' no, no. It had the best ending for us! the people who grew up with Toy Story, I was a kid during the days of Toy Story 1 + 2. Hell I was like 2 years old when Toy Story first came out, so I didn't actually watch it until the late 90's but it was a part of my childhood. When Toy Story 3 came out and Andy was going off to college, it was basically saying goodbye to our childhood for many of us and how we've gotten older. The film was a passing of the torch, to the next generation and I am so happy.
Let the next generation of kids experience the thrills of Woody/Buzz and all the other great characters. There's so many horrible things in this world going on right now, i'd love to see the kids experience a nice childhood like I had and enjoy these movies.
Also think of it this way, by the time Toy Story 6 rolls out... presuming they do a trilogy again, you may have kids by then and you'll take them to see the film that you onced experienced as a kid with your family. It's all about evolution, we got older... so let the next generation experiencing what we once did.