I think a type of PvP would be good to add to the game but done so you don't have to participate if you don't want to. Maybe a PvP between the races elves against humans with varied rewards.
There's a proposal floating around for an Arena. I don't have any problem with PvP so long as I can ignore it,
but I'll get all unhappy if other players are allowed to kick sand in my face.
Acamax has given the right link: all ideas about PvP are gathered in this thread (click). Currently, the idea of a voluntary PvP Arena that's separate from your city has been forwarded. However, other ideas about PvP are still welcome in the referred thread. I'll close this thread as a duplicate.