To preface, I have characters on both PvE and PvP servers, and generally never found much difference between them. While I was leveling on a PvP server I occasionally had the opportunity to chase down horde players, and occasionally got ganked. But the choice was never mine to make about whether I wanted to PvP or not, it was whether I wanted to play with the set of friends on *this* server, which happened to be a PvP server, or a set of friends that played on *that* server which happened to be a PvE server.
With the introduction of xrealm raids and zones though, I tend to focus more on the character I want to play, and have oddly been the the situation where I'm playing a PvE realm character, doing the 'PvP' dailies, and noone's flagged.
Why not just ditch the PvP server concept entirely, and merge PvP-flagged players into PvP zones, and non-flagged players into PvE zones ?
There's certainly no difference in 'community' in PvP and PvE servers that I've been able to distinguish. (I'd suggest the same for RP servers, but there seems to be ONLY community/guild enforced differences in that flag)
Again, I have little personal problem with my level 15s getting ganked on PvP servers (I don't actually quest anymore anyways), I just found my fondest memory of 'world PvP' was chasing down a level 20~ while I was also level 20~ish.
I suppose PvP zones could be level-bracketed akin to BGs as well. It would make for interesting twink developments if a Horde guild decided to invade and hold Westfall while xp-capped. Level bracketing may just over complicate things though.