That would be ridiculous and no one would be able to reach the top of the phone; try reaching above the earpeice to the top left (if right handed) on your Plus holding the phone normally; unless you're Shaq maybe. I have large hands and really awkwardly stretching I can hit the carrier name with my right thumb on the Plus as is.
They may do it with an X Plus type phone, but really you're approaching an ipad mini as the Plus is 6.5" diagonal (if all screen).
And truthfully Apple is really unlikely to keep that old aspect ratio if the smaller X is this new ratio. So to get as wide as the current Plus the new X Plus device would need to be taller than the current Plus to keep the new aspect ratio. It would be near totally unusable 1 handed.
It would be basically a Samsung Note but iPhone version. If they made an edge to edge display phone. With that size screen, and let’s say a stylus style pen. You mean you wouldn’t jump on that? And don’t say no, cause I know you would be full of it at that point. lol