Since there will be updated travel forms for each race, here is what I predict:
Night Elf
STAG
- It is widely speculated that the original intention was for this form to be a stag but was changed at the last minute, explaining the odd hoof-shaped icon...
- Native to Night Elf lands.
- Nelf Moonkin have Stag Antlers, in contrast to Taurens' Horns.
Tauren
TALLSTRIDER
- Native to Tauren lands.
- Striders are tall, strong hunters, like Tauren.
- They are renowned for their running ability.
Troll
RAPTOR
- Native to Troll lands.
- Speed.
Worgen
WORG (Northrend Model)
Obvious reasons.