A Samsung Engineer leaked the fact that he has been working on the next gen Exynos 9820 since January 2018 on his LinkedIn profile. Additionally, the same engineer has been working on a 5G RF chip that is expected to be integrated directly in the Exynos 9820 ever since May 2017. These chips are expected to debut in early 2019.
https://www.notebookcheck.net/Samsung-Exynos-9820-SoC-and-5G-RF-chips-already-in-the-works.295886.0.html