PS Blog said:We’re pleased to announce that the Private Beta program is expanding and will make its debut on PlayStation 4 systems on May 20. If you’ve registered for the PS Now Private Beta, keep an eye on your mailbox for a voucher code.
We are also happy to announce that access to the PS3 Private Beta program will expand to a broader audience in the near future.
http://blog.us.playstation.com/2014/05/19/playstation-now-ps4-private-beta-starts-tomorrow/