They mentioned improving the UI to see players near you but in a different 'phase'.

Quote from MMO-Champion:

Q: Will “phasing” be used more extensively in World of Warcraft: Cataclysm?
A: Yes. We’ve come up with a number of new, cool ways to using phasing since we introduced it in Wrath of the Lich King, and plan to use it more extensively to change the world as players progress. We are also now able to phase terrain, which players will see in the starting areas for the goblins and worgen. We’re also adding some UI improvements to help determine when another player is in a different “phase” from you.
Hopefully the result is something that'll help us.