Anecdotally, at least from several comments I've seen on this forum, the early readers are the ones who later turn out to be particularly strong in mathematics, rather than verbal skills. When tested at age 7, my early reading (at age 2) son was found to be PG in mathematics, but only MG in reading.
I think there is something visual about early reading, or the decoding aspect of it is very non-verbal in the same way that math might be. DS learned to read practically before he could talk, and learned effortlessly. He didn't seem to even care about reading. He was tested at age 6 on the WISC and his PRI was in the 140's (verbal ability a lot lower). Now at age 8 he is still a strong reader but doesn't stand out the way he does in math. He is accelerated 3 years in math.
Anyway, to the OP...I think that most gifted kids who are exposed to phonics and blending sounds will pick up on basic reading at age 5, although I'm sure there are differences in development. I would definitely keep an eye on it if you don't see a lot of progress in the next year, in case there is a reading disability.
