I'd wait.
For one, the next iPhone will be for sale in about 8 weeks (56 days).
For two, I think the iPhone 6 was a weak release; more of Apple self parody than something that Steve Jobs would've allowed to be released.
The 6S should right the ship based upon leaked/rumored specs:
12MP Camera
5MP FF Camera
2GB RAM
14nm A9
7000 series alloy
Force Touch
Less buggy iOS9
Those are big spec bumps, and way over the current iPhone 6 and 6+.