There is no date set yet but they do plan on release an RP PVP Server for the US realms, just like they are going to for the European realms!

Here's what tyren had to say about it on the Blizzars Boards:

To address the large number of concerns regarding Role Play PvP realms, we would like to confirm that we are preparing Role Play PvP service for our customers in both US and Europe. More details will follow at a later date, but we wanted to address the speculation that RP PvP realms would not be offered in the US. This is untrue, and the plan has always been to launch this realm type for both the US and Europe regions simultaneously. We will provide more details as they become available.