At E3, we want to see the gameplay and, more importantly, the Base. Just show us the Base!
When I saw X-COM for the first time, no one showed me the Sectoid, Floater, Muton, or Ethereal. I only knew about the Snakeman and Chryssalid. Seeing the new aliens was always a nice surprise!
Or how about the Shadow Of The Colossus? Do you think anyone would want to play it, if everybody knew what all the Colossus looked like?
No one cares about the aliens! They maybe the weirdest and coolest alien *EVER*, but most of us crazy X-COM fans don't care! Hell, some of the aliens you have are just as cool as the ones in Evangelion, but everyone here (even Codex) hated Evangelion!
If you are just going to show us more aliens (killing the surprise), and no gameplay, then there is no reason to buy this game.