Analyst says that the OnePlus 3 Plus is coming29
While Jiutang didn't mention any rumored specs in his post, we wondered what a premium version of the OnePlus 3 might look like. First thing that occurred to us is that the resolution of the screen should get bumped to 1440 x 2560. A OnePlus 3 Plus would also have to feature a larger screen, perhaps in the vicinity of 6-inches. Because enhancing the display would have a negative affect on battery life, we'd hike the capacity of the cell by 30% to 3900mAh. A Snapdragon 821 SoC might be employed, and a dual camera setup found on the back.
To be honest, this seems like one of those rumors that should definitely be consumed with the addition of a grain of NACL (salt). After giving this some thought, you can reach the conclusion that the OnePlus 3 is pretty much highly-spec'd as is.
source: PanJuitang (translated)