Charlie Stross is agonising in public about whether to write a third book in his Singularity Sky series. Personally I don't mind that the Eschaton is not really explained, or expanded upon. I like a little mystery. If the whole of that universe is wrapped up neatly perhaps it will destroy the feel? After all, look at what happened to the Matrix trilogy, wouldn't you love to go back to before 2+3 and keep that air of mystery?
(BTW my inverse trilogy coolness hypothesis is still on course for coming true. And no I haven't done a graph yet.)