It seems that the Chinese will be the first to make phones with resolutions that are even higher than 1080p, for smartphones, such as 2560×1440. Vivo Xplay 3S is probably the first phone that will support such a resolution on a 5.7" screen size, but we know there's at least one other Chinese company wanting to make a phone with such a resolution, and of course Samsung is considering it for next year, too.
A 5.7" screen size coupled with such a resolution, would put the Vivo Xplay 3S at 515 PPI, which is about 50 PPI more than what the HTC One has with its 1080p resolution on a 4.7" screen. So it's not exactly ground breaking in terms of PPI. However, I don't think anyone was thinking 6-7" devices were suffering for being only 1080p, which is still around the 300 PPI mark for these devices. Even if the improvement is noticeable, there is such thing as diminishing return.
What that means is that the improvement in screen clarify may be too small to compensate for the fact that you now need a GPU that is twice as powerful just to keep up with last year's GPU and resolution, in terms of performance. It also means that even if OEM's can make it so these devices don't have any worse battery than they did last year, that still means their devices have been kept in place in terms of battery life, instead of having improved battery life this year, by using more powerful GPU's and the same resolution. The same is true about performance, which is also stagnant because now it needs to power a much higher resolution.
The Vivo Xplay 3S will also come with 3GB of RAM, a Snapdragon 800 that should have higher clock speeds, a camera with an f/1.8 aperture, Hi-Fi audio chip, LTE and USB 3.0 support. It even has fingerprint support, although that remains to be seen how well it will work, since so far nobody but Apple has done that well enough. The device is definitely pretty feature packed, and considering it will be sold in China, it will probably have a very decent price, too.