I believe the current, updated timeline is as follows, which means Beta will start sometime in the first semester of 2019.
V3 of the Website (Q3 2017)
ElyriaMUD (Q4 2017)
Alpha 1 (T1 2018)
Server Selection (T1 2018)
Settlement / Domain Selection (T2 2018)
KoE (T2 2018)
Design Experiences (T3 2018)
Alpha 2 (T3 2018)
Beta 1 (S1 2019)
Prologue & CoE Adventure Toolkit (S1 2019)
Exposition (S1 2019)
Beta 2 (S1/S2 2019)
Stress Test (Any paid account)(S2 2019)
Launch (S2 2019)