Warhammer's public test server. The 1.4.6 update is designed to tweak both realm vs. realm and scenario PvP. In terms of RvR, one of the biggest changes is the shift from multiple city invasion instances to a single instance. The instance will support 60 players from each realm -- 120 total. "Once that number is reached, no further reinforcements will be allowed," according to the update notes on the WAR website.
Scenario brackets are also being altered. Whereas the old system grouped players into tiers based on character level, the new mechanic uses both levels and renown rank. Players from level one to 15 go into bracket one, while players of renown ranks zero to 69 and 70 to 100 go into brackets two and three, respectively.
[Edit: Clarified 120 total players in the instance]