Wondering how Square Enix is going to go about this for future content patches.

I see it either 1 of 3 ways.

1. They introduce higher currencies for later content.

2. They follow the WoW route in which they convert your current Mythology into Philosophy and convert your Philosophy into gil.

3. They don't touch it at all.

This is also assuming that they continue to trend of having vendor bought gear of a decent ilvl to compliment the highest tier raid at the time.