Tradition dictates it'll be a mythological name. A Roman or Greek god. Or goddess. It depends on its orbit - objects with more unusual orbits are given male names (you'd think a male-dominated profession would save that honour for pear-shaped lady planets with naturally wobbly orbits).
A legend-soaked, mythological name is essential for an authentic, astrological back story! Of course, all the good names have been taken.
So we're stuck with minor deities like Minerva, goddess of cities, education, science and war. Yawn! How about Diana, goddess of wild things? Hymen, god of the wedding feast? No?
Unconfirmed reports suggest they'd like to call it Xena. As in, Xena the warrior princess, the nineties television show. The poker-faced science community does indeed have a sense of humour! Perhaps astrologists will put planet Xena in charge of dominatrix instincts, lesbianism and horseriding.
Personally, I'm holding one thumb for Discordia, named for the Roman goddess of, well, discord. The other thumb I'm holding in the hope that they allocate her chaotic planetary influence to my humble star sign of Libra. Although I'll never admit that I read my horoscope every day (and read it from a different source if I don't like the one published in The Star), it would soften the blow when I stupidly take its advice for gentle-hearted Librans.
Personally, I think any planet that close to Pluto and managing to remain out of sight for so long should be called Proserpina or Persephone ...