BTC from Grayscale is only a part of the BTC supply on OTC. They have sold about 15B USD worth of BTC, while the remaining ETFs have bought about 27B USD, meaning we have net inflows of 12B USD [1]. This 12B USD worth of BTC comes from many sources, including miners and people who choose to sell on OTC at a higher price instead of selling on Spot and causing the BTC price to decrease. I believe that when Halving happens, the number of BTC from miners will decrease and they will not have much BTC to sell on OTC either. Similarly, people with BTC will also want to hold after Halving and this will cause the supply on OTC to be exhausted. And the truth is that there have been days when the OTC supply has been exhausted[/sup].
Of course, Grayscale BTC is only part of the coins flowing into ETFs, but it is difficult to estimate how many coins are available through OTC and what share belongs to miners. It is possible that miners have significant amounts of BTC that they have accumulated over the years waiting for the new ATH and that they will sell them gradually, and that the halving will not have an impact on the amount of BTC that will arrive through the OTC.
Until now, halving showed the first effects only after 6+ months, and it is possible that it will be the same now, and that what you are speculating about will only begin to manifest at the end or beginning of next year.
And even though this buying pressure has not yet been transferred to CEXs, it still has an indirect impact on BTC price through the decrease in selling pressure on CEXs. Another thing is that we only have a maximum of 21M BTC, about 30% of which may have been permanently lost [3], and only about 2M BTC are in good liquidity on CEXs [4]. I think we will see something interesting right after Halving, when the supply on OTC dries up while the investment demand from traditional investors continues to increase.
I do not consider all these methodologies for determining
"lost BTC" to be even remotely reliable, because 30% would be as much as 6.3 million BTC that are no longer available, and I tend to believe that the real number of lost BTC would be only about 10%. Of that, about 1 million BTC is what is attributed to Satoshi mined coins, and another 1 million BTC would, in my opinion, be what everyone else lost.
You should also not ignore the outflows that happen with ETFs, because all those who invest in such a way do it exclusively for profit and sooner or later they will decide to take that profit.