The iPhone 7 could be the biggest update since going from the original iPhone in 2007 to the iPhone 4 in 2010. With iPhone 4, we got a new design thanks to some Gizmodo guy leaking it online, FaceTime, Retina Display (326 ppi), multi-task bar, better camera, etc.
Late 2012 - Nexus 4 introduced Qii charging which was wireless. Something introduced before that with the Palm Pre thanks to Matias Duarte.
Early 2013 - Sony introduced waterproofing on flagships for the masses.
Early 2014 - HTC introduced to us the M8's dual camera setup.
Some of these features have been found on Android for 2-5 years now. These aren't big updates for smartphones in general especially for Android phones which had them for years but they are big updates for the iPhone series. Removing headphone jack and physical home button hasn't happened before either. Having 32gb as a base model and discounting it to $100 hasn't happened either.
Unless the 10th anniversary is truly special or Apple has some big secrets they haven't leaked yet, I don't know how much next year's iPhone will be a big of jump than this year's? OLED? Samsung. Bezel-less? Check Sharp Aquos Crystal and see how comfortable that is to hold without accidental touches with the apps close to the sides. Glass exterior? If it is made in one sheet of glass and one side breaks, do we have to replace the entire body?
The iPhone 7 is the one worth getting while next year's iPhone may not be the one worth waiting for. A Samsung Galaxy iPhone S7s is my gut feeling for next year's "special" 10th anniversary iPhone.