They'll put in a new case and add a new colour.
They'll 'invent' a new proprietary plug that will replace the Lightning and stereo mini plug - but it will only be compatible with Beats.
They'll 'upgrade' the OS that will be backwards compatible with past iPhones - except in one crucial area - which they won't tell you about until the 7 is released and users complain.
They'll include a new feature, but not actually devote any time into the software that makes it work, while refusing 3rd Party software developers access to it to make it viable.
So, really, not a lot will change. And you can only reinvent the wheel so many times...