This is in our future. At some point, we’ll know foreign governments and large international companies are buying bitcoin because the price will rise while the US ETFs are being drained. 
Discussion
What the underlying reason you think the ETFs will drain at that point?
Large international entities won’t trust the US to custody their coins.
This is how I believe it will play out:
The ETFs will fill up as we climb the retail and hedge fund S-curves in the US.
At some point the ETFs will saturate (probably in a few years) as all US retail investors (except the few at the top of the S-curve) have maxed out their core BTC holdings.
The entry of large international entities will create buying demand outside the ETFs.
As the price fluctuates, US holders will eventually sell transferring those coins outside the US. We’ll see this a the ETFs starting to drain while the price is rising.
The chart shows that this is currently happening with the gold ETF in the US. The gold ETF is draining while the price is rising. This implies that foreign buyers are taking possession.
Good thesis. Makes a lot of sense. Things are getting juicy.