As Aulayna mentioned, Beta Test Phase 3 will begin in "early June". They have not yet announced the official start date. Since they've usually started them on Fridays, my best guess is Friday, June 7.

In Phase 3, you will be able to import your character from version 1.x if you have one. Progress will be wiped at the end of Phase 3. You will then be able to import your character again for Phase 4. That progress will be saved and will carry over into official release. However, beta servers are not the same as the final release servers. You will choose a new server again when the game officially releases. No worries about trying to match everything up in beta.