Why start so high? The story of the next expansion will start at level 80. Some people will want to play it on the new jobs(whatever they end up being). Starting 10 levels below the story gives the players both a chance to learn the class before being tossed into unfamiliar content and a reasonably short grind so they dont have to wait too long to catch up.

As for class quests, whoever teaches the new class to us will have some sort of drama going on and we will be involved in it. Story wise, most people will be past the ShB point where they need to have completed their role quests(and for the ones who arent and choose a new class, theyll just get an extra quest for exp every couple levels). The next expansion is highly unlikely to be set on the first, so their wont be any continuation of the current role stories(the ones ive done all seem fairly well wrapped up as well). As for whether returning to the source will see us back to doing individual class quests or whether role specific tales will be told, its impossible to say. They could even combine them(say with class quests at 85 and 90, role quests at 80 83 and 88) if they wanted.