So, what do we learn? A rumor doesn't have to have much substantiated evidence to get spread around like wildfire - it just has to be something people WANT to believe.
Would a double-album, with more to come today or later be great? Yes. Is it likely to happen? No. But, that is why I started the rumor - because I want to believe.
On a happier note, Radiohead LP sessions have always included a large amount of additional material, released later as EPs, single b-sides, bonus discs or 2nd LPs (in the case of Amnesiac). So, any way you slice it, this surely isn't the last we have heard from the King of Limbs sessions.