While the Samsung Chromebook Plus is expected to arrive next week with 4 GB RAM on board, its Pro sibling is scheduled to arrive in April. While it is supposed to feature up to 8 GB RAM, the latest rumors claim the Chromebook Pro might get a 16 GB RAM variant after a while as well.
http://www.notebookcheck.net/Samsung-Chromebook-Plus-might-have-up-to-16-GB-RAM.196134.0.html