Oligopolization happens from time to time when productivity growth decreases. Firms are forced to downsize, merge, acquire and consolidate to shrink the levels of capital and labor they invested in when projecting forward into a future with the baseline assumption of higher productivity growth.
ML in its current form - efficiency optimization across a ton of different vertical industries - is also a reaction to decreasing productivity. If you can't grow your revenues, you need to shrink your costs, and ML/analytics do that well.
Once we see a new technology or infrastructure driver that jumpstarts productivity growth (distributed electricity, refrigeration, plumbing/running water, public roads, combustion engines, more recently the internet and mobile phones) startups will be able to once again flourish and will be able to return to the public markets with their own company/brand rather than look for acquihire exits as many do in the current climate.
Something that makes sense to me would be some form of basic human sleep/energy acquisition optimization. We spend 1/3 of our time asleep - is there a way to use VR/AR to enhance productivity during this time, or to avoid it altogether without killing us? It seems unnatural, but many facets of our current lifestyle would have seemed unnatural to someone 50, 100, 200 years ago.