This ending explained contains full spoilers for Toy Story 4.
Toy Story 3 seemed like a perfect ending for Woody, Buzz, and the rest of the gang. Andy went off to college, but he left his beloved toys in the gentle hands of pre-schooler Bonnie, implying that his toys had many years of playtime left ahead of them.
Toy Story 4 director Josh Cooley admitted that when it came to approaching a fourth installment, “We had the same questions everybody else has right now: ‘I thought you guys were done.’ But we had those questions five years ago when we started… We love the end of Toy Story 3, and feel like that’s the completion of Woody and Andy’s story. But there was more Woody story to tell.”
Source: IGN.com Toy Story 4 Ending Explained