I suppose that that might be a theoretical ultimate endpoint, but usually what happens is that instead of "nothing" what you end up with is "something better" (or at least "something else"). In the case of blind salamanders, the "something better" is a lower-maintenance, less injury-prone body surface. Eyes are vulnerable to all kinds of things, so if a species with eyes finds itself in a context where having eyes imparts no advantage, their greater vulnerability to injury (and perhaps also things like freeing up cerebral real estate and caloric requirement), may actually cause eyeless mutations to win out in the longish run, as they seem to have done here. But that's not nothing, it's something better for life in the cave environment.

To me, "nothing" is what will remain when all conscious life dies out.