I think the definitions will evolve with time. It is now becoming clear that our classic definition of "planet" was far to narrow. But that's ok and our language will evolve.

Speaking of evolution: When it becomes feasible. I hope we can image "twin planets" orbiting a nearby star. It would be really awesome if we could find 2 earthlike planets orbiting the same nearby star!

Such a place would be ideal for the evolution of a true space-faring species. Imagine if the moon and earth were roughly equal in size and both had breathable atmospheres! Were that the case, I would think that we would be well on our way to colonizing both worlds! (Or THEY might be well on their way to colonizing us!)