I agree with you that if the system providing no block reward or very few rewards (like transaction fee). The monopolizing process can move very very slow, even for years.
Actually it depends on how much fees the minority stakeholder pays. If he doesn't make transactions, he will remain with same percent of the stake.
Nevertheless, the stakers taking care of staking reward may dissatisfy with this unfair mechanism since the smaller they are, the lower ROI they will obtain. As an example, the current individual miner (with ~0.5% staking power) can only obtain ~0.3% incentives if mining independently ...
Well, if the rest 99.5% are owned by a single account, yes. But that's unlikely in practice. If, for example, the rest 99.5% stake is distributed to even smaller accounts, the guy with the 0.5% stake should be getting more than 0.5% of the blocks.