No, as far as I've seen no new missions come into play, though even right now the reputation they give is very valuable. A good fraction of my Champions of Azeroth rep has come from repeating the mission that can give you 850 rep a pop.

Also, azerite is azerite. Once your reps are all done, 300-odd azerite every time you visit the mission table is nothing to sniff at.

You can use the profession items to upgrade the rewards, though they're pretty expulsom heavy and, as such, quite expensive at the moment.