The question runs up against that wall because it relies on the idea of the state and its relationship with that decision to be made. People thinking that we'll slip into a post money economy aren't really comprehending the pressure built up already in millions of people. This initial stress won't be initial, it won't feel preparatory for a bigger thing precisely because it will be the big thing for people already suffering. And this is just the employment issue, saying nothing of debt. The "we," in other words, don't necessarily wait in the same way. It might very well be there are riots long before the question of UBI is ever imagined as a state solution--including when it's necessary. It's imagined as a sort of conversation between the public and the state where a large group are simply jobless and demanding for something when there is no work. But the road to that is long since begun and there are too many people already who are breaking in different ways (see Le Pen, Golden Dawn, Trump, Brexit, etc), whether articulated through migration, dead industry and unemployment, colonialism and all the shit that it brings, race and gender wars currently underway, and so on. Any number of those buttons, including debt, including war, might get pushed on the way to that moment of "we want jobs" - "there are no jobs" and "now what?" By that point the question is what the state even looks like anymore. Not even does it de facto take care of its people, but why wouldn't it try to exercise more strict control over them? See the police for an example, as some people know better than others. The point is that I don't even think we get to that point if only because it's a path that ignores these other things putting stress on the state and its relation to the people. The road to that point is more likely to act as a breaking point for whatever issue is in play, and by that point I have no confidence the state remains the same.