A pen isn’t really a necessity for navigating the menus of a phone like that as long as it’s designed properly, and lately some companies have been exploring the specific field of improving UI navigation for large-screen devices without the need for additional input methods.
There have been efforts in this direction from companies like Microsoft and Apple, and we’re likely going to see even more solutions coming in the future. The smartphone market is still evolving after all, and we’re probably barely scratching the surface of what’s possible with these devices.
The S7 will likely come with some significant improvements of its own, especially if the device is released next year. Samsung will have plenty of time to perfect its design until then and experiment with some interesting new features, and they are one of the companies that like to innovate most. There are already plenty of rumors about what the S7 is supposedly going to bring to the table, but of course at this point most of them can likely be disregarded.