The video's use of the Texas grid is a very good one, because Texas works almost as an electrical island. It's a shame they weaken their claims by pointing to places like North Dakota and Iowa as having successfully achieved over 25% wind, however; neither of these states operates as isolated power systems. Indeed, both import or export substantial amounts of power depending on wind conditions. The same holds true, albeit to a slightly smaller extent, with the European examples cited.
I also take issue with the "no end in sight" claim for continued cost reductions. Every energy technology has worked its way along a downward-sloping cost curve, but in every case the curve's decline slows. In particular, even if solar cells were free, there is a non-reducible cost of assembly and installation. I don't see how we move substantially below $1500/kW installed in solar.
One final note: the video correctly notes that a key to the success of high penetrations of renewables is diversity of resources and locations. Even if solar panels are very cheap, we can't run the system with solar alone. Some combination of solar, wind, marine, hydro, hydrothermal, demand response, energy efficiency and storage can work.