It can get worse or better, yes. Most of the time, it gets better because we learn more about how to cope. When it gets worse, it's often because you've become more stressed than usual, and now have fewer mental resources to deal with the flood of sensory input or the challenge of social interaction. Physical illness can also make it harder to deal with autism.

Dramatic changes in symptoms usually only happen during childhood, though. In adulthood, it's usually a matter of what else is making your life harder or easier.