Despite offering twice the storage, it's still the same size as the 48-layer V-NAND-based 256GB eUFS Samsung launched in February previous year. There will always be use for large internal storage space - as media files increase in size because of the proliferation of 4K content, and as data connection speeds get better so that you can now download files with larger sizes.
Samsung has just announced that they are now manufacturing new 512-gigabyte embedded Universal Flash Storage (eUFS) for flagship smartphones and mobile devices coming next year. Even though the 512GB eUFS solution contains 2x the number of cells as compared to a 256GB eUFS, Samsung states that the "inevitable increase in energy consumed" will be minimized by the 64-layer 512-gigabit V-NAND's "advanced circuit design" and new power management technology in the controller.
MicroSD storage seems to be the main target with this innovation, as Samsung suggest embedded storage is more stable and and less limiting than current external storage cards used in mobile devices. It is going to change soon, you will be seeing 512GB storage on the smartphones, especially, the Samsung flagships. Nothing is impossible these days.
On a side note, Samsung also announced plans to increase production of its 64-layer 512 Gb V-NAND chips as well as 256 Gb V-NAND chips to meet growing demand for mobile storage, SSDs and other products.
Of course Samsung's and other Android phones sometimes have the option of expandable storage through a MicroSD chip, but internal storage has its benefits.
With 512GB of eUFS storage, Samsung says that a flagship smartphone would be able to store approximately 130 4K Ultra HD (3,840 x 2,160) video clips of a 10 minute duration.
As for speed, Samsung says that the 512GB eUFS is able to offer read and write speeds of up to 860MB/s and 255MB/s, respectively. The new eUFS can also read 42,000 IOPS and write 40,000 IOPS for random operations, which is about 400 times faster than a microSD card. Still, we do know Samsung has a habit of using a bunch of similar specs on these two classes and we don't expect anything different come 2018.