Well I'd agree with this statement, and disagree at the same time(about having nothing to do at lvl 80). What I suggest, if you feel that way, to set up a small goal first, like do a PvP reward track, or get all ascended trinkets.. then it gets more tense, since you realize what stuff you haven't done yet- infused trinkets, ascended armor, legendary weapon, did u try to mash up an über looking armor? I mean, there are alot of possibilities, just Arenanet is bad at telling you what to do now.
The things stated above, you can get them trough almost any kind of content. Now beside that, you've got meta achievements, and living story S2 is coming tomorrow which is gonna be quite awesome.
At the end, it is true though, because of the horizontal progression(better looking gear, not better stats) you feel like u have nothing to do when you achieve max stats. That's why I put GW2 aside, and just play it when META or LS has to be done, and play Wildstar instead.