Do you think that new discoveries about how Pluto interacts with the solar wind suggests that Pluto should be reclassified as a planet?
Yes, we will, but for a different reason. The problem with the current definition is that there are only eight known planets in the entire universe. If Planet 9 truly does exist and is found, that will close the books on the number of planets in the universe. Those 3300 things that we have found orbiting other stars are not planets, at least not by the current definition. A planet is, first and foremost, something that orbits the Sun. A proposed modification to the definition of what constitutes a "planet" drops the notion that a planet is something that orbits the Sun (it just has to orbit a star). It maintains the notion of "clearing the orbit".Definitions are silly and there will always be exceptions. Astronomers looking at little Pluto would do nothing different if it were considered a planet. As time goes by, we'll probably have to dump the definition we have now.
If Planet 9 exists, is observed, and is anything close to the size scientists currently think it is, it will be deemed a planet. Here's a graph:What if Planet 9 really is out there where it's thought to be? It's thought to be much larger than Earth, but will probably not have had time to clear it's orbit fully yet.
While I agree with the general thrust of your post, I think this one's a bit too strong a statement. Yes, it's impossible to observe directly, but knowing the mass, and providing the object is not in the very low-mass end of the spectrum (and all exoplanets detected thus far are way above the threshold), you pretty much can tell if its gravity could make it round or not. That is, the 'potato radius' is calculable, and even for purely rocky objects it lies well below what is currently detectable as an exoplanet.It's impossible to detect the shape of exoplanets using extant or near-future technologies.
That's the key point of the proposed modification to the IAU's definition of what it takes to be designated as a "planet". Unless those newly discovered objects are made of unobtanium, they will necessarily have pulled themselves into a spherical shape thanks to self-gravitation given that they have sufficient mass to clear the trajectory. The spherical shape aspect of what constitutes a planet is superfluous. Clearing the trajectory is anything but superfluous. Orbiting a star and clearing the trajectory are the keys as to what differentiates a planet from a non-planet.And all exoplanets detected thus far are way above the threshold.