It is my opinion that WoW Style Raiding is not the be-all and end-all when it comes to MMO end game content - this was just the method WoW used to keeping its fan base very well but not every MMO has to follow these rules to be successful. What also hinders players opinions is that other MMO's have failed to sustain their fan-base when deviating from this model and not conforming to a Raid based end-game BUT these games did not have the answer for alternate end-game progression e.g. starwars online and guild wars 2.
I believe an RvR end-game system does basically the same effect as raiding, it creates those elite players that people look up to, like the 'best' WoW PvE guild members on a server. It rewards those who are highest skilled in solo/group AvA/RvR with additional battle skills which replace the 'WoW top tier gear'. Look at DAoC as one of the very few examples of this with limited PvE, this has survived for many years. I believe ESO will encapsulate this along with other rich end game content to further supplement.
Also... its not like there will be NO PvE... ESO will have an element of group PvE; it has been announced there will be rewarding dungeons which will require a group with bosses. The most exciting of there is there is the "DAoC Darkness Falls" equivalent This is a dungeon in the PvP/RvR, which in DAoC was controlled by one faction who was dominating RvR capture points. When the tides turned in the battlefield (Cyrodiil) the dungeon would close for the factor who lost control and open to another, now dominant, realm. This would in turn allow the newly controlling faction players to enter and begin farming the illustrious loot while in turn sparking a number of battle between the players trapped inside when the realm control switched. HOW MUCH FUN DOES THAT SOUND!?!
Albeit there will not be scripted raid fights consisting of 40 organised people standing in the correct place wiping and repeating. Earning points and collecting loot that overpowers any grind-able PvE or PvP/RvR solo/small group content. This basically alienates people who dont join guilds!!
just my 2cent.