This. All these clones do is help WoW in the end because of the following:
1) Inevitably, a new develoepr can't release the amount of content WoW currently has to keep the bunnies running on their treadmills and happy with the game. They start to miss WoW and it ends up being a free advertising campaign.
2) WoW turns around, looks at what each new game introduces and then adds to their own game to appeal to that audience. The Firelands were their answer to Rift's open grouping, and earning ExP in their battlegrounds was from War. I wouldn't be surprised if MoP came out with voice acting and a bolster mechanic for lowbie PvP.