Maple Magician Shields will be more valuable in the future?

No it hasn't.
Potential system was created to revolve around the limitations set by job advancements. Just because something is created with boundaries in mind does not mean that those boundaries changing automatically changes a system that doesn't have any relation. Limitations on potential is not guaranteed to change at all, but apparently none of us would be surprised if it did.

I misinterpreted what I was quoting. Of course job level has no affect on potential tier, but they have coincidentally always fell in the same range. Based on that, there's no reason not to hope they won't be coinciding again.