First, new aspects are totally possible. GW writes the fluff and can ret-con anything, having a new aspect complete with new Phoenix Lord for them and saying they were there since the founding of the Asurya would not be unusual for GW.
I can see the aspect warriors getting consolidated into generic FOC choices as upgrades to the entire squad, in the same way that the current Eldar Pathfinders are simple suqad-wide upgrades to Rangers.
And as the Aspect Warrior boxed sets automatically come with an Exarch now, I foresee that Exarchs are automatically going to be part of the squads, not optional upgrades.
Ie Having a single elite army list entry "Close Combat Aspect Warriors" where you choose the gear of the squad to make it either Banshees or Scorps. The current codex does this, since both HB and SS have the same statline and the only difference is the wargear, really.
"Ranged Aspect Warriors" choose either Fire Dragon or Dark Reaper
"Fast Aspect Warriors" squad choose either Warp Spiders or Swooping Hawks
Dire Avengers an upgrade to Guardians?
Shining Spears are upgraded Guardian Jetbike squads?
Likewise, I can see the Wraithlord being a character upgrade to a squad of wraithguard.
This would slim down the number of FOC entries in the army lists CONSIDERABLY. It really wouldn't matter much to us players in the end gameplay wise, but would make the army list look a lot more streamlined.
I forsee see Falcons, Fire Prisms and Night Spinners being a single FOC entry as well as coming squadrons - just like the variants of the Leman Russ entry in IG. GW needs to get people to buy more Falcons etc, and limiting Eldar to only 3 or so skimmer tanks would hurt sales. Or if one of the new units is another Falcon variant, have a squadron of Falcons and/or it's variant be one Army List, and have the Fire Prism and Spinner be another Army List squadron option.
Remember the rumors for 6th ed is that you can drop FOC slots for new ones (ie limit yourself to 1 heavy slots to be able to take 4 Fast attack)
The trend since Codex Blood Angels is for all armies to have at least one flier, so the "Vampyre" is probably a new Flyer, likely a smaller plastic version of Vampire Raider in the same way the Storm Raven is a smaller version of the Thunderhawk.
So here's what I predict the Army List will look like:
HQ
- Phoenix Lord (probably a generic HQ now, and you choose which wargear to make it a named character)
- Farseer(I see Farseers having different levels of power now, from "Warlock" to full on disciple of Eldrad)
- Autarch (maybe Phoenix Lord is an upgrade to this?)
- Avatar
- Solitaire (If they keep him as uber as he was before, I totally see him being an HQ to prevent people from spamming him, and to have him compete with other HQ)
- Exodite Lord
- Seer Retinues
- Warrior Retinue (could be for Autarch or Avatar as the court of the Young King)
Elites
- WraithGuard (and Wraithlord)
- Harlequins
- Close Combat Aspect Warriors (either Banshees or Striking Scorpions, possibly a new Exodite themed close combat Aspect?)
- Ranged Aspect Warriors (either Fire Dragons or Dark Reapers, possibly a new Exodite themed aspect?)
Troops
- Guardians (option for Support Batteries, and Dire Avengers as upgrade)
- Rangers (Pathfinders as upgrade)
- Assault Guardians / Exodites on foot (I see them as being the same entry)
Fast
- Scouting Aspect warriors (either Warp Spiders or Swooping Hawks)
- Vyper
- Jetbikes (Shining Spears as Upgrade)
- Exodites on lizards
Heavy
- War Engine of Vaul Squadron (Falcon & a new variant)
- Siege Engine of Vaul Squadron (Fire Prisms & Night Spinners)
- War Walker squadron
- Exodite on Big Dragon (total guess, probably the new kit)