My guess is that actually the ITCOTCK set would be it's own thing, with Blu-ray and possibly new unearthed material. And that the three following albums would comprise it's own box, not unlike the one coming out at the end of this year.
"In the Wake of Poseidon" and "Lizard" will always be odd-balls when it comes to the box set releases as neither album was made with a touring lineup, and they really don't fit with either "In the Court of the Crimson King" or "Islands", but I would still rather have an "Islands" box set released next year rather than tread a lot of the same ground again with "In the Court of the Crimson King". They could wait a few more years before doing more with that album again.