I think he is referring the the "iPhone 6S" to be the second generation of the iPhone 6.
Basically the 6 is a redesign (new model) and the 6S would then be the second generation.
I think we all know what he meant
To be safe, one should only buy the last revision of the old version. For this year perhaps an iPhone 5s. By the same reasoning, if you run Windows you should run the last revision of the previous Windows version, or the one before that.
Seriously, that kind of thinking just drive me nut. I used to work with a guy who still shot film as of a couple of years ago. I looked at his scanned photos and held my tongue. Life is too short. If the latest hardware has what you want and you can afford it, why wait? A few bugs is a good trade off for new features.