There is zero inclination Apple is releasing a second version of the Airpods in September. Considering they didn't officially launch in December 2016. Not to mention stock related issues still for those experiencing finding a pair. I would not hesitate to purchase a pair now if you find them available.
There is absolutely a zero % chance a refresh comes anytime soon. They are (seemingly) just now inching towards being able to meet demand. For the next year or two, we will probably just see some additions via software. A product design refresh won’t be until at least 2018 at the earliest.
I agree with the rest. Especially if the watch was any indicator. It's 1st refresh didn't come out for something like 18 months after it became available. Also - I just bought a pair tonight, so.....got get em!