Is the saltwater hobby coming to an end?

To an extent. Marticulture is really a win win for everyone and is working well, but that goes for corals, not fish (yet?). Ban fish collection in Hawaii and then someone else will collect the same fish and sell it elsewhere though, if they can. Perhapse we can limit import to the US, but the rest of then there is the pesky rest of world

Really though, the whole thing is ridiculous, there are much, much larger threats to natural reefs... Keeping a highly redundant, genetic library, spread out in homes across the world, doesn't seem like a bad thing to me, but that is another debate.