larger iPhone, or be sold as an accessory, remains to be heard, but the insiders tip that “Apple is preparing to launch the phone as early as 2019."
We've heard from two different sources already that Apple might be prepping a 6.46" display iPhone, perhaps with the current iPhone X design, but larger screen diagonal, and that's where the eventual stylus could be heading. Since the stylus-ed phone may come with the 2019 crop, there is plenty of time to come up with a new all-screen design for the iPhone XI Plus or whatever it gets named, too, and with a truckload of applications for the pen.
There are numerous ways to take advantage of one on a larger display, as exemplified by Samsung's Note line, but somehow we doubt that Apple will take this approach - any alleged phone-sized stylus would probably be sold as an extra accessory, what do you think?
source: Korea Herald