Do others agree with this assessment?
You are probably right about the extremes balancing each other out somewhere in the middle, especially as the bitcoin ecology grows.
The last assumption however, that inflation/deflation rate should tend to zero is not a given.
The overall inflation/deflation rate depends entirely on how much request for bitcoin there is to do its main business, which is to be used as a payment medium.
Large changes in user base will inflate/deflate the currency.
Double the user base, and you will roughly double the value of each coin = deflation.
Cut the user base in half (because - let's say - users leave for a different bitcoin implementation) and the value of each coin will roughly be half = inflation.