They are going to release freshly exclusive rewards with the new crystal conflict mode, you should be looking foward to those (which I'm sure are going to be very cool because they'll want to bring as much incentive as possible to the new mode).

I think both approaches are respectable here, but I'm more on the side that previous rewards shouldn't be made available again, because it will cheapen the exclusivity of both past rewards and future ones (as it'll set a precedent).