This article was actually written by me
Oh ok - haha.. Thanks for the correction. I appreciated the clarity and focus you put forward in it. I will update the post.
With steem, the overall size of the userbase influences the distribution of the rewards to posters and curators, so as the userbase decreases, the witnesses have more ability to access more inflation. In any case, I understand what you are saying and it makes sense - I did think about that too but figured that if the top witnesses are the main engineers building projects from the SPS then their ability to draw steem to themselves multiplies not just from the direct payments but from their increased ability to generate profits from other steem holders who are now their customers. This could, in my untested thought process, lead to the point where domination might become a more genuine concern. The same did hold for bid bots and their operators but maybe won't in the future. The other issue is psychology and public perception - even if there weren't a mathematical risk of domination, many investors will not invest if they think there is such a risk.
I'm not sure that true decentralisation is possible in a profit generating system that is itself run by members within it who are competing. I think a distributed network where everyone has equal power to compute and co-run the network is the only true solution to the equation. :)