My personal opinion is when the suspect behaviors are troubling, and you're also seeing them in multiple settings.
If he's only acting out in the classroom, then maybe the problem is only academic match. If he's only inattentive in one sport or activity, maybe it's just not his thing.
You're right that highly intelligent children tend to have a lag in executive functioning that resolves itself, but even if that is the case, there's no harm in getting help while his executive functioning (EF) are legitimately lagging behind age peers - or his other abilities.
The posters above are correct that highly structured physical activity (marital arts) and music are very good activities (therapies?) for learning to direct one's attention.
If you choose to have him evaluated and he is diagnosed with it, you still get to chose what to do with that information. Some parents do nothing, some use medication, some use the information to get accomodations in the classroom. None of these decisions are permanent.
When my son was first diagnosed, I chose medication. It was AWESOME! He couldn't do his schoolwork without it. Now, 2 years later, he can function in most environments without medication and cognitive behavioral therapy is more effective than medication. So, for now, no medication. Just take life one phase at a time and don't worry to much about what hasn't yet arrived.
(((Hugs)))