http://www.techradar.com/news/the-samsung-galaxy-s9-may-not-have-microsd-slot-and-heres-why

The Samsung Galaxy S9 is one of the first flagship phones we're expecting to see in 2018, and we've started to hear a few interesting bits of speculation about it - including a hint that the next generation of Samsung phones won't offer support for microSD cards.

That's hasn't come from anything we've heard from the Samsung supply chain, but rather it's the logical conclusion to the news that Samsung is now producing 512GB flash memory modules using the new eUFS (embedded Universal Flash Storage) standard.