your argument is about FIAT exchanges which has nothing to do with bitcoin code or blockchain transactions. yea exchanges can cause issues and the exchange rate on exchanges can change. but thats a failure of the FIAT greed. not bitcoin.
I don't think so. Regardless of whether or not fiat is the unit of account used to express Bitcoin's purchasing power, Bitcoin's purchasing power will still be subject to fluctuations. Even if Bitcoin becomes the universal money, if the demand to hold Bitcoin decreases, so will Bitcoin's purchasing power. (Although from a practical perspective, at that point, we could expect far, FAR less day-to-day volatility.)