Honestly I'd rather hope one of the 2-CD sets is the Rozsa Polydor albums. There's no reason they can't fit, and the only reason to make three is either because of stupid legal issues or "to keep the integrity of the original albums".
At this stage I'll happily take three separate CD releases, even at Japanese import prices. Will it ever happen?
Personally, I don't see what's wrong with keeping "the integrity of the original albums." Each is a classic that is meant to be heard on its own.
I doubt that third disc would add cost to us. Licensing and transfers seem to be what really determines that.