Have you incorporated the Ron-Shamir Entities into this? The paper's a little dated and it's unclear whether the balances on pg. 11 are still accurate, but it'd mean at least two additional billionaires.
If I recall correctly, the paper is from the time when bitcoin was trading at about $10. With my rake model, these entities have since shed 70% of their holdings, on average. I have included 350k DPR hidden stash and 400k mystery owners + all that I believe beyond reasonable doubt have 100k or more. The rest is statistics. The difficult part is that we don't know if for example Winklevoss have sold a part of their coins or not. They are sitting on 10,000% gains and their price projections are conservative so they may not be über bull.
The possible existence of large hidden holders is something that cannot be ruled out, still. The 400k may be 1-2M if somebody has a masterplan. At any rate it does not affect the rest of the distribution, and due to bitcoin's crashy nature, even economically I don't think these pose a threat. They are in position to do wonderful things though upon coming public
