I read the first price for bitcoin was determined by the electricity cost required to mine a block and from that people would have calculated how many bitcoins for $1 and so on now we are into one bitcoin for $2500+
Similarly why not we switch over to calculating how many satoshi for one dollar. I believe there will be exchanges to be ready to adopt and provide trading facility based on this. As per preev, right now $1= ~4000 satoshi.
Why this :
Stocks trading has a tradition of spiting. Read more on split here :
http://www.investopedia.com/terms/s/stocksplit.asphttps://en.wikipedia.org/wiki/Stock_splitThis is not exact split, but I believe this will serve the purpose of splitting.
Let us discuss,
What are pitfalls we may face if we switch over to new unit.
What will happen suddenly an exchange will provide trading based on unit satoshi.
More importantly how it will influence bitcoin price levels.
This already happened in 2013 on Bicoinity when they changed from the Bitcoin to the mBTC. At the time it meant that 1 mBTC was 1 USD, which was nice.
The Satoshi is too small to be meaningful. No one wants the penny or cent to be broken into 40 parts, it is pretty pointless as it is now!
So to answer the question, I would see that the µBTC could be used when 1 BTC is worth over $100k USD, so 1µBTC is 10 cents.
The Satoshi should be used when Bitcoin is over $10mil, which I guess would mean that the USD is already pretty much dead anyway!