The WoWhead blog says that there are new hairstyles on the Patch 4.2 PTR
It also says that there have been new 'dos on the PTR before that never went live, so we won't know if there really will be new styles available until patch day. If there are new styles at the barbershop, I'll definitely be updating the version of the Azeroth Beautician's Manual of Feminine Style
that I posted on my blog.
I'm most excited about the Braided Tail for Blood Elves, both new Dwarf styles, both new Troll styles, the Night Elf "Sassy Tails", the Orc "Bangs", and the Tauren "Omega" horn style.