Pre-alpha experiences are scheduled to happen at a variety of times. Caeoltoiri responded recently to a similar question here
For quick reference:
- Pre-alpha experiences ◃ Where we are now
- Alpha 1 (aka Closed Alpha, under NDA) wiped
- Alpha 2 (aka Open Alpha) wiped
- Beta 1 (aka Closed Beta, under NDA) wiped
- Beta 2 (aka Open Beta) wiped
- Exposition (aka the world-building phase)
- Launch
I can only add that the UNOFFICIAL dates for the next parts of this process (domain and settlement selection), are currently pegged to happen in a couple of months. I would say ATM that a comfortable ballpark guess at getting our first actualy whack at pre-game experiences might happen around mid-June? (Which would be fine for me, that's around my birthday.)