When there are more users whales won't be able to get anyone near the front page.
Fact is if 80% of the stake votes together, they can influence which content goes on the front page.
You presume all whales are benevolent. Stake will eventually end up in a power-law distribution, because perpetual 100% debasement is not sustainable (even the transactions fees of the entire earth could not support it).
but the more you divide things up into more pieces, the more likely it is that the number of whales present in any given segment will be zero.
Hypothetically the solution is to divvy up by like-mindedness, so that no group can collude to control all the rankings. With k-means, it is impossible (unless you can somehow game the algorithm by splitting up your accounts) to have your voting power in more than one of the k clusters simultaneously.
I do worry though that the power-law distribution will always find a way to win.
Even if we allow users to control their own clusters (e.g. via a Follow button), the power-law distribution may influence which users they are exposed to.
I'd suggest adding some randomization.