If the number of coins in circulation goes down, a number of things can be done to offset the effects of deflation and maintain the velocity of transactions. For example, smaller fractions of currency can be introduced into transactions, however it would be annoying to have to constantly count a bunch of leading zeros.
No need to count leading zeros. If the common denomination gets that small, people will naturally migrate to millibitcoins and then eventually to microbitcoins.
Why count the leading zeros in 0.00126 BTC, when you can simply refer to 1.26 mBTC.
I'd certainly expect to see a price of 2.83 µBTC rather than 0.00000283 BTC (or at least I'd expect it to be displayed as 283 satoshi).