No one can dictate what all the exchanges and wallet software providers will do, so a variety of approaches will be tried.
This brings risk when a user accustomed to a particular decimal point location switches to another client. A user in the habit of typing "100" for 0.1 BTC may accidentally overspend by a factor of 1000.
I did this in the reverse just the other day. Felt pretty bad as I did not want the person to think I was ripping them off during my purchase. This hatchet cuts both ways.