They better be careful, though, or else we'll have another Pluto situation where we try to classify something and end up classifying it out of its own category.
1. We know 9 planets in the Sol solar system
2. Oh shit, there are way more of those small ones, where do we draw the line? Is there a thing differenciating a big asteroid from a planet?
3. Let's go with (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.
4. Pluto doesn't satisfy (c)
5. People get angry without proposing their own criteria
c. Has cleared the neighborhood around its orbit excepting Pluto.