If the discovery is confirmed, this is probably going to reopen the debate of whether Pluto should still be considered a planet. A few years ago, The Rose Center for Earth and Space generated a lot of controversy when one of their permanent exhibits only listed eight planets in the solar system. Enough people asked about Pluto that they added a plaque explaining why they had not included it. The Center's director, Neil deGrasse Tyson, wrote an essay called Pluto's Honor (1999) in which he explained Pluto's demotion. Tyson noted the following:
As citizen Tyson, I feel compelled to defend Pluto's honor. It lives deeply in our twentieth-century culture and consciousness and somehow rounds out the diversity of our family of planets like the troubled sibling of a large family. Nearly every school child thinks of Pluto as an old friend. And there was always something poetic about being number nine.
As professor Tyson, however, I must vote--with a heavy heart--for demotion. Pluto was always an enigma to teach. But I'd bet Pluto is happy now. It went from being the runt of the planets to the undisputed King of the Kuiper belt. Pluto is now the "big man" on a celestial campus that occupies a larger tract of the (outer) solar system than that spanned by the eight planets.
Where do I stand on this? More with sentiment, I'm afraid. I've used Pluto's bizarre status as a teaching tool, but even so, I grew up with the notion ingrained in me that there were nine planets. I still remember the mnemonic I learned in fourth grade to remember their order: My Very Earnest Mother Just Served Us Nine Pickles. (Of course, at the time, Pluto's orbit had brought it closer to the Sun than Neptune, but let us not quibble.) I would hate to see Pluto reduced to simply one of a new class of smaller objects.
But...if astronomers start to find other TNOs larger than Pluto, I guess I'm going to have to change my mind. So, in some way, I'm rooting for this discovery to either be unique or a mistake. We'll see what happens.