I think a classic Jump Potion like the one being used in WoW would be a bad idea. It takes a lot of the charm away from the game and it leads to people never exploring certain parts of the game which is the opposite of what an MMO should deliver.
If you never explore the world around you then you also don't really care much about it.
Instead what they should do is: Make it so that Main Story Quests are shortened. By that I mean the player would skip all those fetch quests and get much more exp for the quests that actually remain. If done right then even casual players should be able to catch up in a day or two but still get to experience the world around them instead of just buying that potion and sitting on their butt, having no idea of the awesome locations out there.
If you never explore the world around you then you also don't really care much about it.
Instead what they should do is: Make it so that Main Story Quests are shortened. By that I mean the player would skip all those fetch quests and get much more exp for the quests that actually remain. If done right then even casual players should be able to catch up in a day or two but still get to experience the world around them instead of just buying that potion and sitting on their butt, having no idea of the awesome locations out there.