I imagine that in the next decade, the USA (and California in particular) will learn that there exists a tipping point where a homelessness crisis turns into proper slums/favelas/shanty-towns. The middle-income and developing world is replete with examples of this happening, and America is foolish to think itself immune. Since the current trajectory of increasing economic disparity and insufficient home construction in desirable areas is likely to continue, the result should not be any surprise.