Has to be bigger than Earth's Moon??!!
I like Chris' idea, 8 planets and the rest being "Plutonian" objects.
Unless a larger object which is round and has a more circular than ellipsoid orbit is discovered. That should be classed as a planet.
As far as always considering Pluto a planet, for as often as I consider Pluto it wouldn't matter. I don't turn off the lights, for instance, and ponder Pluto.
Arf