There will no longer be such a thing as a gold mission reward.
And followers with that trait will instead have it changed to a buffed scavenger trait, further increasing their gain of garrison resources.
It is rather wrong to say it is a -100% nerf, because that was not the entire gold income from the garrison.
However worth noting is that also the salvage yard will not be awarding "player equipment" - basically no more BoE's as far as I understand it, and the class sets are going to be reduced to minimal vendor value, so that salvage yard will remain attractive still for the sets or achievement progression, but little else I think.
But what will determine the viability of the garrison for gold making will depend I feel on the professions.
How much demand will there be for WoD crafted equipment, and subsequently the materials.
Transmog demand I think will drive that to a large extent.
Some people are heavily banking on there being a strong demand for the hexweave bags still.
Due to catchup mechanisms, there is effectively no need for those materials as a means of skilling up.