The below is from Reinhart's translation of a summary of the new Famitsu:

・１クラス１ジョブ対応
・対応しているジョブとクラスは経験値共有　ジョブにチェンジした後の経験値もクラスに入るため気軽なジョブチェンジが可能
・ジョブチェンジは対応クラスが３０であれば　受けられるクエストクリアで可能　
・その後レベル５刻みでクエスト発生　試練クリアでアクションを覚えたり専用装備をもらえたりする
Job
- 1 class 1 job
- For supporting job/class the exp is shared, when changing to the job the exp gained will go into the class so you can change job easily
- for job change if the class is level 30 you can clear the quest.
- After there will be quests every 5 levels, with each quest clear be able to learn new action or obtain specific gear
So it seems you will be capped as far as levels go, but we'll only need to go back and do five quests to tap their full potential.