It came to be known through Samsung's official Analyst Day presentation slides that the company intends to bring Ultra HD displays with 2160 x 3840 pixel resolution to market this year. At the company's roadmap workshop last year Samsung hinted once again that it has UHD smartphone displays in the works. These displays will apparently have a non-standard pixel matrix arrangement referred to as diamond pixel. Given that the pixel density will be record high it's not like users will be able to notice individual pixels.
According to a new report Samsung is going to introduce the UHD display with the Galaxy Note 5 which will arrive later this year, in the fall to be precise. Production of the UHD panels is expected to start by August which would make sense as Galaxy Note handsets are traditionally unveiled at IFA in September. Galaxy Note 5 is said to have a 5.89-inch display with 748 pixels per inch. Apparently a dual edge variant will be offered as well, it's 5.78-inch curved display will tout a record high 762 ppi. Keep in mind that these are unofficial claims and should be taken with a grain of salt for now.