The final cut of the 9th episode of the Tesla Motors Club Podcast, featuring Chad Schwitters, the former president of Plug In America, is now available. You can watch it now on YouTube or listen to it on all major podcast networks.
I was invited on April 10th to configure RWD. The AWD is still locked for me in the configurator. My guess is that a lot of employees and Model X/S owners were lining up for that option. If the availability does not start until July, I could see many of the "already invited" to wait a month or two, to get the AWD invite.
Seems like only one round so far. Doesn't appear to take into account if it is prior owner as many non-owners have received AWD config. Elon stated it would be based on time you placed the reservation.