Is it possible a child with high functioning autism would show signs until close to 3 years old?

It's possible that a: Child with autistic spectrum disorder who acquires a large vocabulary but doesn't use it for age-appropriate reciprocal social i communication & has overdeveloped pattern recognition & rote memory is perceived as being precocious in developing preschool skills, while his non-compliance for non-preferred tasks, perseveration in preferred tasks & stereotypies are perceived as personality traits.

Yes: Some children who are less severely affected may not be identified until age 3 or later. They may appear to have a speech delay, attention problems or behavior difficulties but not to an extent that they have a diagnosis.