We've already heard from Microsoft employees that the reveal is going to be hardware orientated, they might not go into the detail that Sony did but I'm pretty sure one way or another we are going to see specs on the reveal date.
I posted this before somewhere else I think but I think it's gonna go like this...
#XboxReveal: Vision, brand, some game demos (no tech demos, this is going on Spike, remember), entertainment service details, brief hardware summary, E3 teaser trailer.
E3: Games, world-premieres, exclusives, demos from devs, more details on entertainment services.
BUILD: Specs, deep dive on the guts of the system, SDK, apps/indie support, etc...
Gamescom: Launch plan, pricing, availability, and maybe a look at 2014's lineup.
On a slightly unrelated note, I had a dream last night that
Rainbow 6: Patriots premiered at Tuesday's event, so make of that what you will...
