I'm not sure. It depends on the scriptwriters and the direction the story takes.
Yes, Andy is not in Toy Story 4. By this time, he has grown up and passed his toys on to other children.
Andy in Toy Story 1 is thought to be around 6 to 7. This can be inferred from his play habits and the toys he has.
Andy was around 9 years old in Toy Story 2.
Andy doesn't appear in Toy Story 4, so his age isn't relevant in this movie.
Andy doesn't have a major role in Toy Story 4. He's grown up and given his toys away, including Woody, at the start of the movie.
The voice of Andy in Toy Story is John Morris.
Andy was around 6 years old in the first Toy Story movie.