I believe Yoshi-P has stated he will not go beyond the 2 Job per 1 class plan.

However, there are plans for future class/Jobs requiring players to first reach a certain point in at least 2 or more Jobs before they can unlock those class/Jobs.

For example a Fencer class (class going into Red Mage) may require a lvl 50 BLM and lvl 50 PLD Job quest to be completed first before you can unlock Fencer class.