Many larger holders I know would not ever sell BTC. They would be inclined to hold it, and either mortgage it or use some kind of financing in fiat currency, based on the BTC as the underlying asset.
As to when it will hit 1m, I think that year 2024 = 500K is quite feasible. From there is just a double to get to 1m.
Of course,the volatility of the cryptocurrency is great, but now bitcoin is one of the most popular assets in the world, so its price will fluctuate within small limits and will only grow