Speculation about upcoming flagship phones is in many ways like Christmas; the planning and mention of them is getting a little bit earlier year after year.
So, to be a complete hypocrite about it, let's speculate on the Samsung Galaxy S10, which would be due out sometime around Spring next year. So, over at The Investor, a Korean publication, market analysts have been touting the underwhelming sales figures for the S9 as a reason for Samsung to push the envelope with the S10. Bear in mind that this is very early feature speculation, but one of the bigger features that is being mentioned is the possibility of a 3D sensor. This sensor would open the phone up to a variety of software that could make use of that sensor; 3D mapping, AR emojis, etc.
The 3D mapping feature alone would open up a wide range of features, allowing your phone to map out a room in a way that's easily understandable for computers to understand. This means that your phone could tie in with Augmented Reality, as well as providing assistance to other smart home technology.
So, all of this is purely speculation, and this feature line up will likely change 10 times between now and then. You know what though? Speculating about these things is fun.