Not surprisingly, most of the hyperlexia research and even the posts here focus on the very young children. There is very little in terms of "what to expect" for older kids who grow out of their ASD label. The hyperlexia-IQ research shows no increase in IQ compared to average, but the research mostly focuses on ASD population with and without hyperlexia.

The hyperlexia clinic in Illinois (CSLD) says that recruiting kids for hyperlexia type 3 studies is very challenging because they are very rare and difficult to identify at a young age (differentiate them from ASD kids), so a large practical longitudinal study has never been done.