Arenanet have issued this video with game director Colin Johanson in which he details what's next in Guild Wars 2 over the coming months. While Johanson mainly gave general statements such as "taking the existing gameworld and making it as strong as we possibly can", putting emphasis on making sure there would be plenty to do in old areas for longtime players.
They will be adding more dynamic events, building new rewards system to motivate players to go back and explore these more fleshed out areas. Players can also expect more of the "live story lines" or themed events (Wintersday, Lost Shores are examples of this), and Johanson says they've learned lessons on how to do these better. The core systems will also be revisited with new features added to world vs world, and PvE, and an expansion of PvP (making it more accessible and with a stronger sense of progression, plus tools to grow the competitive side of Guild Wars 2).