The beta world is cleared
No date fixed yet. It is announced here when there is one.
Everything earned during the closed beta is wiped before the world opens properly. Announced with notice, not sprung on the day.
Closed beta progress does not carry over. Accounts, units, currency and progression are all cleared before the world opens, and the operations sheet has said so from the start.
This is worth saying twice rather than once, because a beta that keeps accounts across restarts reads like a beta that will keep them across launch. It will not. Persistence in this phase exists so that a bug in loading an account can be found, not to bank a head start.
The date is not fixed and it depends on when the world is ready to open. It is announced here with notice, and it will not be the first anyone hears of it on the day it happens.