Two key notes.
1. The cross realm phasing only applies in low population zones. Immediately following the release of the expansion don't expect to see cross realm people in the leveling zones of Pandaria simply because there will likely be sufficient people from your own server to consider the zone "populated".
2. Even if cross realm introduces PvP players into the same zone as PvE players, this wouldn't actually cause PvP to occur since the PvE player still would have to opt-in to be PvP flagged.
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.