There is no information right now. They're keeping quiet so far.

However, I'm betting they'll be like Classes, but called Jobs anyway, with standard abilities at the same levels as a class plus additional abilities unlocked by quests. Unless they plan on having two different levelling paths depending on whether you're raising a pre-expansion class, the new jobs will probably be very similar to the current class/job combos, including cross-class skill slots (ie: 5 total that can be filled with specific abilities from two other classes).