Pluto a Planet again? Is anything a planet?
My sense is "yes", but then I am in the liberal "of course Pluto is a planet" camp... but then I'm in good company on that one. Phbt.
See here and here
More seriously, it is clear that the IAU will be re-visiting the definition of planet soon.
And for mostly impure motives (hint: changing the definition so that a planet is only something orbiting a main-sequence star is not going to help anyone convince the Academy that they should get the Nobel prize. Chasing the wrong variable, as I understand how the process works).
This is going to be a bad and nasty process. On the other hand, the community does need to decide whether to go with a traditional, and possibly inconsistent, phenomenological definition; or to go with a consistent physical definition that may be undecidable for any given object.
It is somewhat aesthetically objectionable that under the current definition, a perfectly nice planet, like the Earth, would cease to be a planet if we were to be inadvertently ejected into interstellar space. The Earth as a sub-substellar object just doesn't sound right just because there is some accident of orbital mechanics.
WGESP IAU definition
The Berkeley definition
Note the "stellar remnant" variant. Under one definition, when the Sun exits the AGB phase, the planets cease to be planets, even though they were planets for 9-10 Gyrs. But if a planet is ejected through dynamical instability at any point, it ceases to be a planet under either definition.
On the other hand, no one seems to want a low mass object formed in isolation to be a planet; even if it quacks like a planet. And phenomenologicall it'd be impossible for the foreseeable future to untangle the dynamical history of free floating planet-like objects.