I want to assume the next step won't be as grindy and might involve dungeons of other bits of old forgotten content. Start from Great Gubal Library through all the 60 dungeons. Then 3.5 might involve running through the HW 24 man raids for a new item.

Though I'd be fine with light grinding. Or, and me and a friend were talking, one of the next steps might involve those hard fates in the early levels that no one does anymore like the giant crab in Costa, and the giant plant thing in the East Shroud. They're good EXP for people who level but they require lots of manpower to down.