The long press has always been nice when developers integrate it. But they don't always. First of all long-pressing a home icon currently is how you start moving them. So this would give an extra capability. But second of all—especially dealing with more complex interfaces and content—Force Touch gives you less of a margin of error for activating it. Sometimes the finger lingers on the screen. This UX interaction is more deliberate and would have a proper API. I'm not certain if there is an API for long-press or if developers roll their own code for that. An example is Tweetbot long-presses on the top back nav item quickly goes all the way back to your timeline if you've been clicking deeper into content. Tweetbot is also a good example of an app that has lots of custom design and interactions so they probably made it themselves.
Furthermore this could potentially open the doors for future iPhone models to remove the home button. It's going to happen eventually as devices are always simplified and reduced where possible to save space.