Blizzard posted the following this evening regarding the beta servers and downtime.

Emergency Update: Work Progresses on Restoring Servers
Blizzard network engineers are currently testing server hardware for any indications of damage. We hope to have a thorough test completed within the next 24 hours and by then provide a more extensive update of when we can bring the servers back online. Initial reports indicate that all vital data is still intact, meaning players should be able to pick up where they left off.
Players will be able to receive rest bonuses for the time that their characters have spent offline. However, auctions will have expired by the time servers are brought back online. Thanks for your patience and concern for World of Warcraft through this challenging time!