My understanding of PS4 Beta

[Orophin]

From my understanding, since we're not using our live characters in beta, we'll still be able to access them on the PS3 until Phase 2 starts.

I would think your account on the subscription servers would still be active until live service for PS4 accounts start. I haven't seen anything saying that once you start PS4 beta testing you won't be able to play the PS3 version.