I think Pluto will remain a planet for sentimental reasons. If we accept Sedna as a planet then there will be millions of applicants eventually.
Titan, one of Saturn's moon, is actually larger than both Mercury and Pluto...at the Astronomy.com forums someone argued that it should be labeled a planet as well. But then what about our Moon, it is quite big.
I guess we need a more precise definition of the term "planet".
Tormod
