I’m with you about the danger of the national sales tax growing, but I think this is less likely since it is very visible, unlike income tax hikes which are invisible.
But I have NO SYMPATHY for people who pay no taxes now as per your example. Everyone should pay something, instead of half the population paying NOTHING.
That visibility really shouldn’t be overlooked. There’s a reason that Michigan’s sales tax hasn’t been raised for so long. Its political suicide to do so.