Unfortunately Persephone was already used as an asteroid's name... so it probably won't show up again.... too bad, as it would be a perfect name.
The story is that the group from Cal Tech who discovered it was only using Xena and Gabrielle as code names, since "2003 UB313" and "S/2005 (2003 UB313) 1" are a couple of mouthfuls, and have never intended for them to be the planet and moon's real name. They have a name picked out, using the tradition of gods or goddesses of creation myths that all planets are named after. It just probably won't be Greek or Roman, since all those are pretty much used up...
The IAU took this chance to decide once and for all what a planet is. Since the naming convention depends on whether UB313 is a planet or not, they're waiting until they decide what UB313 is before they formally accept the name.
But, as I said, it did make for an interesting Astronomy class... I divided the planets into 3 groups: Terrestrial Planets: Mercury, Venus, Earth, and Mars; Jovian Planets: Jupiter, Saturn, Uranus, and Neptune; and Trans-Neptunian Planets: Pluto and 2003 UB313.
What was funny about it was that my students just dutifully wrote down "The solar system has 10 planets" while taking notes, and not one of them said a word until I said "Nobody finds that odd?"
Here's the actual journal article announcing the discovery:
http://www.gps.caltech.edu/%7Embrown/papers/ps/xena.pdf
