It is confirmed that the S9 is coming out. So far we have heard from https://www.tomsguide.com/us/galaxy-s9-schematics-design,news-26254.html that the main difference from the S8 is the size. We have heard that the S9 is bigger and thinner than the S8. They also said that the S9 will have a dual back lens. This is relates with mechanical and electrical engineering and the website is down below.

https://www.tomsguide.com/us/galaxy-s9-schematics-design,news-26254.html

https://www.youtube.com/watch?v=DKKsZoguPuA