I don't think there are plans for open chat channels (of the type we see in MMOs); but there might be an alliance-wide comms mechanic for ships in the same instance, so they can co-ordinate during a combat engagement, for example. The in-game comms is quite versatile - you can limit it to predefined messages (like those you'd use with npcs), ship-to-ship text, or ship-to-ship voice chat.@ Cathy
Once again, I don't think that will happen in ED, and I explain why lower down. But would you agree that a guild channel in chat (or whatever comms system we have) would be a useful thing?
I imagine that most serious alliances will go outside game to voice chat (Ventrillo, Mumble, Teamspeak and the like), just like traditional MMO guilds do. Those set-ups persist outside the game, of course, so there's continuity for members of alliances between game logins there.