Many of the poster of those replies seem to forget that there is already 35W Quad Core 3612QM which is a TDP the 13" rMBP & cMBP can handle just fine. The 3520M is also 35W and both CPUs reach that TDP at some point due to the Turbo mode. There isn't really any difference.
The only reason I can think of why Apple doesn't is because they want to keep a bigger performance gap between the 13" and the bigger margin much more expensive 15". The socket is no different and the cooling can handle 35W TDP. If those chips were exchangable you could just swap the CPUs yourself.
The only reason they didn't do it is because they don't like how it looks in their portfolio.
I doubt they can escape it in the next release with Haswell. I would guess it is marketing. They wanted people to focus on the great display of the rMBP and keep the notebook cool and the standard MBP not be too much competition for its more expensive brother. They kept the Quad Core out so they have a new killer feature for the uninformed at the next iteration. Next iteration there will almost definitely be a Quad Core in both 13" MBPs as an option at least.
The Air on the other hand definitely won't see a Quad Core until 14nm Broadwell at the earliest, when there are single SoC Quad Cores around. Not only because of heat but also because the chip needs the right kind of packaging.