A lot of dissent has been expressed regarding the implementation of transmogrification into PVP. The bottom line is, its going to happen. PVP gear will be transmogrifiable into other PVP and PVE appearances. Essentially the biggest impact on PVP is players will no longer have the ability to visually read their opposition and will have to assume at the start of a battle that their opponents are at least as equally geared and skilled as they are and will have to feel out their enemies' strengths by actually engaging them rather than simply seeing what gear they have and venting to your teammates whom to go after first.
This adds a layer of complexity to PVP that had never existed: The fog of war.
For many, this will be simply too much. Conditioned to reading appearances and adjusting, many teams will see their ratings slip while the more intelligent and adaptable teams will excel. As someone that PVPs, I find it a boon when someone underestimates me, thus I will transmogrify my high-end PVP gear to look like crafted starter gear to both lull and distract my opponents. Thinking I'm an easy kill, the weak and cowardly will attack, only to find they're about to be served up with an apple in their mouths. The elite killers may pass me over going after a perceived higher threat, only to find I hit a little harder than they bargained for. Nope, looking forward to the new PVP, its certainly gonna mean you have to think on your feet and adjust mid-combat.
The flip side also means you will see more psychological warfare introduced. The obvious is under-dressing your gears appearance, but also having a team of people wearing what appears to be starter gear or older season gear mixed with people wearing the top end current season gear. Who do you go after? The elite looking one or the one that seems to be making an effort to fall back, is it a feign? Is he really that weak? Or is he a distraction? A trojan horse? You gotta be looking forward to this if you really enjoy PVP that's challenging.