Well, assuming it's a Warhammer esque type scenario, it means that the bulk of content is generated from a PVP perspective.
So, look at WoW, where the primary content development is in PVE. Dungeons, Raids, and other PVE experiences easily receive most of the attention, with BGs and Arena being more of a side endeavor. They're constantly running balance corrections, of course, but you rarely see new content or new importance lent to the system.
In ESO, there are... 3?... factions, iirc. And the top ranking player in the world gets to play as Emperor or something, with some limited power associated with the job. And it seems like that factional aspect is going to be a big part of everything.
I'm sure there will BE PVE content. I know they've discussed dungeons. It just seems like the game is trying to champion the PVP side of things. And, IIRC, dungeons are sort of "public" instances (no clue how that works), but I feel like I remember them mentioning you could run into other players in your dungeon. So that could have a PVP aspect too?
GW2 is another PVP-focused game. There ARE plenty of PVE activities, but the real endgame is the PVP stuff.