Why will it happen before 2020?
It's unsustainable growth, and I'm afraid the crash is going to happen sooner rather than later.
Will it be as bad as in 2008? I don't know. But it's going to hurt (except if you're wealthy enough to invest heavily right after and ride the wave back up again).
QE was a reaction and counterpressure to low rates, not the cause.
Stuff we actually need like housing, healthcare (in the US), and education have been rising faster than 2%.
Assets too like stocks have risen much higher as well.