The 2015 iteration of the iPhone is expected to have new features like Force Touch, which the company recently introduced in the Apple Watch, but won’t have a multi-camera system. According to a report by appleinsider, there will be a 4.7-inch model and a 5.5-inch model, and will be called iPhone 6s and iPhone 6s Plus, respectively. It’s likely that the iPad will have Force Touch in the next model year. How Force Touch works is pretty simple: different touches will perform different actions on the Watch (and possibly the iPhone). Right now, the rigid display of the iPhone won’t support Force Touch.
As for the two-camera system, it’s out for the 6s series because it would require an overhaul of the chassis and we all know that the “s” upgrades aren’t fundamentally different than their predecessor. Adding a camera would also require a re-design of the entire interior in order to make room. Most updates come as hidden internal or software changes.