One of the best features in GW was the instant travel. Having just finished Volume 1 in Lotro, I wish a lot of other MMOs took this feature and ran with it. Since GW2 is more open world, I'm fearing this system is going to get curtailed. They have explained that roads between outposts should be relatively clear except for times of blockade type events; this doesn't confirm or deny instant travel, though it would affect the initial travel to discover an outpost. On the other hand, with the introduction of events, there’s the possibility of expansion to the instant travel system.
Map travel between outposts could be plotted out, like the way it happens in WOW at flightmasters, except the travel would be at most 30 secs duration. As progress is made along the route, any events that occur in the surrounding area pop up on the map as icons that could be clicked on by the player to interrupt travel and instantly travel near to the event in progress. This would be a nice system to combine both instant travel and event notification.
Another option is to allow players who are taking part in an event to broadcast the event to friends or people in their guild, and then giving them the option to instant travel to that person. The location could be close to the broadcaster but out of aggro range. To take that concept further why not allow a player the option to broadcast an event to other players in the surrounding area, it would be a nice way to allow sociability and getting people together to experience events.
Lastly what I think is the most likely, is NPCs in outpost allow for instant travel. A farmer's son is in an outpost waving arms about, shouting about an attack on the farm, the player talks to him to instantly travel near to the farm. There could be heralds in cities that have the same function, but indicating major battles that are occurring, maybe a town-crier in smaller posts. I just want to see a load of NPCs vying for attention, the so described 'hundreds of lions running all over every street of the city'. These are only the small touches, the nuts-and-bolts of events are the hard part but have the best confidence in Arenanet to pull it off.