All of the old ones will be! You can buy your basic Poke Balls (Poke, Great, Ultra, etc.) when you collect certain badges. By talking to certain NPCs or finding them, you'll be obtaining all of the old balls you could find in Sinnoh (Repeat, Timer, Quick, Dusk, etc.).
The Master makes its obvious return TWICE; One form Professor Juniper, and one as a gift from an NPC by trading Pokemon with 50 different people.
Nothing new really, but all of the old Poke Balls you loved before are back!