This isn't gifted research and not new (2010), but as I just came across it I thought it might be useful to post. This link below is an article which describes a study comparing "early" to "late" readers and the age at which their skill levels merge. Relevant in that it is nice to know what educators may point as data to support the frequently heard statements, "they all catch up" and "early readers don't stay ahead".

Briefly, the study compared children who were taught to read starting at age 5 with those who were taught to read at age 7 and found they read at the same level by age 11.

http://www.sciencealert.com.au/news/20100401-20448.html

Polly