The Worlds Adrift site has been updated with the news that the Early Access program will be starting slightly later than expected. Bossa Studios said that the game needed a bit more time in development before releasing to Steam for Early Access. Worlds Adrift will officially enter EA in Q1 2017.
The letter goes on to inform fans that the Alpha 5 playtest is imminent and hopefully can be as early as next week. The Alpha 5 will have several new additions since the last.
You can read the full details on the Worlds Adrift site.