I'm a little surprised how quickly people believed that everything will be instanced and ruin the game. The reality is that we still have no idea how SOE will handle things and it is way too early to make judgements.
I see absolutely NO way SOE would shoot themselves in the foot by making ALL PvP instanced. There has got be some primary form of PvP in place that's either open-world or area-limited or otherwise. Same goes for dungeons- there will surely be plenty of officially-created dungeons located in the world to explore. And rest assured, the entire world will probably be ever-changing, adaptable, moldable, and destructible.
The instanced PvP/dungeons mentioned are almost certainly just ADDITIONAL PLAYER-created content (battleground or dungeon maps). Such non-professional, non-moderated content likely has to be instanced because (a) there is simply no room for it all on the world and (b) it would have way too much potential for abuse. There is just no other viable way of doing it. Plus there may even be certain advantages to instanced battlegrounds- like maybe you can create your own rules that would have otherwise not been possible on the Norrathian landmass - things like teams, capture-the-flag, duels, who knows?
As for housing, again the instancing does not mean it's ALL instanced. For example: there could be a limited number of houses available in the persistent world in addition to instanced housing. Or there could be instanced plots that contain several houses. Remember, SOE has plenty of experience with housing from EQ2, so I have to imagine they know what they're doing and would not simply take the easy way out.
Bottom line is we just don't know yet until reveal. And SOE certainly still knew how to keep the GOOD secrets away from the public.