It doesn't feel that long ago that LPDDR4 was released, but Samsung announced its first chips back in 2013, since then with both PCs and Phones using DDR4 there has been a growing shortage of supply leading to an exponential growth in the price of DDR4 RAM. Things are starting to settle down a bit now and there could be fines for some companies that may or may not have price fixed.
This week Samsung has announced the successor to LPDDR4 with a completed fabrication, functional testing, and validation of a prototype 8Gbit LPDDR5 module.
The company is targeting data rates up to 6.4Gbps-per-pin with the new memory which is twice that of the original LPDDR4 that was released or 50% higher than LPDDR4X. This has been combined with reduced power consumption via a lower Vddq I/O voltage and other means such as deep sleep mode. Samsung is claiming there is a 30% reduction in power usage from the new chips.
With many flagship mobiles using 4-6GB of memory, it is likely that next year or beyond we will start seeing a lot more 8GB based chips.
Some news sources are suggesting that the Samsung Galaxy S10 could be the first phone to include this chip, and it certainly is possible, but my opinion would be it is highly unlikely. Samsung has only just developed the chip, it is not ready for mass production yet. Looking back to LPDDR4 Samsung made a similar announcement in December 2013 but from what I can tell the first chips to include this were the Snapdragon 810 and Exynos 7420.
The Exynos 7420 was found in the Galaxy S6 which was launched on 10 April 2015, similarly, all the Snapdragon 810 phones were announced or launched in 2015. So following the same timeline it would likely be over a year before we see any LPDDR5 based phones while the Galaxy S10 will likely be launched early 2019 around MWC time.