What I would like to see in future is generally new branch expansion to multiplayer mode, which will add another dungeon to explore (deep roads or primeval thaig), new characters to play, new missions and bosses to complete/defeat.
So, starting up from characters I would like to see:
Dragon hunter - someone coming from Pentaghast family, experianced hunter who will be especially specialized in fighting against dragons (more resistance for their attacks, flames; some kind of dragon rage - increasing damage of hunter attacks for some time when dragons, drakes, dragonlings etc. die nearby). I think that he should be a rogue, but using long forgotten combination of sword and dagger.
Grey Warden senior - he would be a warrior using heavy armor and shield, increasing resistence of the team of darkspawn attacks. He could be as well more powerful when fighting darkspawns.
Dreamer - as a mage I would like to see a woman here. Because of most of Dreamers live in Tevinter, she could have their origin there. I'm not sure however if she could be an elf, who gained freedom because of respect to her powers. Dreamers would gain more physical resistance and possibly gain power to mind-control oppontents.
Now, what about new dungeon:
I would like to see deep roads or primeval thaig because in my opinion it would match quite nicely to Inquisition goals, especially if we are talking about destroying sources of the red lyrium and stopping the darkspawn from going out to the surface. Naturally every faction already avalible would be able to appear there, but darkspawns (emissaries, hurlocks, genlocks, shrieks, etc.) would be meet very often.
Boss of the deep roads could be some kind of alpha-darkspawns (possibly something new, like darkspawn triumvirate? I mean the battle against three of them: genlock, hurlock and emissary and minor of their kind).
I would also like to see some new quests to do on the dungeons, for example something like destroying the source of red lyrium.
Of course I know that the topic is mainly about possible new classes, but I hope that nobody has something about some other ideas in my post.