I think the biggest problems are Scourges, Hellions, and Reavers. Reavers, the only real thing they need is a second attack, and then they'd be good for harrassing heavy weapons squads in the back.
Scourges need to be made into a fast attack choice, and lose the option for dark lances, and maybe gains some new weapon options (I love splinter cannons, but an anti marine weapon would be nice too). The prices for their guns needs to drop as well.
Hellions... they just need to be made a little cheaper. And get assault weapons (Something like shuriken catapults would be awesome).
If these units, and maybe even the talos as well, get buffed, I'll be happy, even if they do nerf some of our better stuff. I just want a bit of variety here.
On the other hand, if GW decides to go the whole nine yards and overhaul the DE into a beginner army, then I'll be royally pissed... I'm something of an 'Indie kid', and the reason I started out playing DE (they were my first army) and stuck with them, instead of selling them like every other newb, is cause I like being the only dark eldar player in my gaming group. If a ton of newbies started buying dark eldar, I'd probably just sell them and start a new army.