I also think that the third runway (at least to the north of 27R/09L) is a blind, will never happen and is a non-starter. I know the area referred to by A and C, but if built in this strip, that would leave the A4 and its hotels and other commercial facilities standing between the new runway and the existing 27R/09L, and I do not believe in a million years this will happen, or that those buildings will be razed. Not to mention the problem of bridging the M4 spur, unless the new runway stops just before the spur.
All this is possible, I suppose, but I doubt if it is safe or desirable. And in the prevailing westerly conditions, how will aircraft taxi to the eastern end of such new runway without taking a ground tour of much of the neighbourhood