Deflation pushes the ultra-rich utility curve to flatten out and,
I'm not sure how you are supporting this claim. What evidence suggests this?
The big difference is that this will most likely be political power as opposed to financial power since there won't be any currency to manipulate.
So you say, but this is not a so dissimilar scenario to the hard gold standard employed by the US leading up to 1913, and then JP Morgan met with some senators to draft the federal reserve act and laid the groundwork for the modern banking dynasties.
A) How much power is effectively a result of the manipulation of a currency's value?
B) How much can bitcoin be actively manipulated by the bitcoin ultra rich in a hypothetical bitcoin economy?
These are very difficult questions to answer. Those who can/could do those things with bitcoin, or have with fiat money in the past, are not exactly forthcoming about it.