Ultra-low yields on Treasuries will be a slow-moving global financial earthquake - until now, they still offered global investors some scraps of risk-free return.
In the years to come, we can expect new heights of bipolarity and schizophrenia in markets. Yields on stocks, bonds and real estate will be driven to clear bubble levels that can't be remotely justified by any fundamental risk-return analysis, only by comparison to guaranteed 2%+ annual inflation losses on cash. Governments will be forced to buy a wider and wider array of assets, in larger and larger quantities, after smaller and smaller declines or bouts of volatility - "portfolio insurance" provided by central banks, guaranteeing the accumulated fortunes of the rich.
I suspect the ultimate endgame is an array of new taxes on capital, estates, wealth, financial transactions etc. to keep things in balance by stealth confiscation and redistribution, rather than market based mechanisms (including price declines, investment losses etc) as in the past.