One of the most important things that will happen in the next 50 years is probably global population decline.
Most of the people I talk to think that the Earth is set for a population explosion, but that mode of thinking is several decades out of date. By about 2050 (in less than 40 years), given current trends continue, population will begin to decline. My guess is that it will occur sooner than that – perhaps 2040. So, as far as we can tell, marginal indigenous population collapses like we see happening already in countries like Japan, Korea, Germany, and Russia will be happening all over the globe in about a generation.
The following documentary called Demographic Winter is an introduction (from a specific point of view) to the general topic. It was published in 2008 as far as I can tell: