The presenter didn't say its unlikely, he said and I quote "It won't happen tomorrow, and it may not happen at all". It's a small, but important difference. Yes, new technologies are expensive, hence the scale of economies.
Not sure what your point is with pumped hydro. I am familiar with systems where excess power from renewables during the day is used to pump water into an area, then when required, that water is released back, spinning turbines, creating electricity - an ingenious way to "store" energy.
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