Air vehicles are always a possible update, doubt a specific class just to use them would be added though.

As an Eldar I'd play as a Dark Reaper, though I'd love it if they implemented the forge world Phantom Spectres http://www.forgeworld.co.uk/Warhammer-40000/Eldar/SHADOW-SPECTRES-ASPECT-WARRIOR-SQUAD.html

avengers for me. if eldars are anything like the tabletop army. they wont win in a fight at close quarters against the best of the empire. unleash the shuriken storm and watch them fail their saves!

Sith Juggernauts ftw.

Reapers, dragons and if they have it shadow specters but more than any aspect I'd like to pilot falcons, wave serpents super heavies or nightwings

For me personally, I'll be playing either Warp Spiders, Striking Scorpions, or a Ranger.

I like Farseer is but Warlock is way more my style. Playing as a Warp-Spider could be GREAT fun too though.

Striking Scorpions or Warp spiders

Dire Avengers without a doubt. A shimmershield and a power spear if I ever get the opportunity to play an Exarch.

Striking Scorpions, obviously. If they won't be available then Dire Avengers.

Both have a very iconic look to them.