Samsung already confirmed that MWC 2018 would see the unveiling of the next flagship Galaxy S9 and the Galaxy S9+. According to Evan Blass, famous for his leaks on Twitter, the company will announce the phone on February 26. A "C-level executive at a major casemaker" said pre-orders will begin just three days later, on March 1. The actual shipment and global release would happen on March 16.
According to a C-level executive at a major casemaker, the go-to-market schedule for Galaxy S9 / S9+ is as follows:

Launch - 2/26 Pre-orders - 3/1 Ships/releases - 3/16 — Evan Blass (@evleaks) January 16, 2018
In 2017, the Galaxy S8 arrived a month later than usual, but this time the Korean manufacturer is getting back to its 2016 release frames. The new flagship is expected to come with Exynos 9810 chipset, stereo speakers and dual camera for the Plus version. The smaller one will have only one 12 MP camera, but it will come with a variable aperture that switches between f/1.5 and f/2.4.