I am thinking the HCHII might already have caught the Prius. People on this site seem to agree that the Prius dash reports 1-2 mpg too high, whereas the HCHII displays 1-2 mpg too low. Depending on how many report "by display", "by hand", or "by hand and display, mixed", the HCHII could already have passed, in real figures. Maybe someone could make a search in the database, find out the relations, and make an estimate.

And I too think the HCHII figures will improve further, they are improving almost every day I look, whereas the Prius figures are stable.