It would be difficult for him to reach 1.1 mil, but I fully expect MS to sell a large number of shares into SP500 inclusion (and by doing so partially or completely negating the inclusion rally).
In this scenario, he probably would be able to sell $30 bil or so (or whatever is left in his ATM) plus maybe 1-2 bil more in preferreds, so up to 300K btc more is possible, bringing it to almost 900K, then maybe slowly selling the rest of preferrds for quite some time, reaching 1-1.1 mil. I don't see him selling 100K of that until years (or a decade) later because it would immediately collapse the stock premium.