There is not going to be any further updates to itch.io version as Raft will be released into Steam Early Access sometimes this year. The Steam version will support Multiplayer Co-Op by allowing one player to act as server and others join his game.
"Raft will release on Steam Early Access in 2018 with multiplayer, reefs and much more new content and features! To be notified when it launches, please visit our Steam page and press 'Add to your wishlist'! We are not releasing any new updates on Itch.io as we are working towards a Steam Early Access release. To read more about this announcement, visit our Blog!"