More quests are definitely in the works, and always will be(for all levels as well).
Content will also be added all the time, that's a given. Some of the content will evolve etc as well. An example of that would be the recent removal of Versikol(a dragon added recently to West Wastes for a quest series) due to him being part of a bigger story than just giving out quests.
And yes, with recent improvements to the quest engine, there should be some really cool quests coming. I think everyone that's done the Newport ring series can attest to the fact that not everything will simply involve looting the corpse of a specific target.
So I think this is a good opportunity to also point out that we're still hiring some quest designers to shore up positions left open since the server has come back up. Take a look at the stickied thread if you're interested in applying.