I don't know why people keep repeating this stuff, because it's not true at all.
The 13" has much more thermal headroom than the current 35W processor it holds (see Anandtech's review, the thermals section). The 15" has to throttle when running it's 90W CPU and GPU full tilt. At full tilt the 13" doesn't even run its fans at max speed, let alone throttle. The fact that the current 35W processors don't even touch the thermal roof of the 13" makes going to 28W a pretty baffling decision.
There is also plenty of space- unlike the 15" there is nothing under the trackpad in the 13" currently just wasted space.
There is no, I repeat, no technical reason the 13" couldn't handle a 45W quad. The thermals could handle it, there's enough room and the battery shouldn't see much change unless you're doing heavy lifting which you shouldn't be doing off battery anyway. You might actually see battery improvement since there is more room for throttling and a higher performance per watt ratio.
I would love to see a 2.0 (BTO 2.3) quad iris pro in the 13" while the 15" gets the 750m which we know it will now. It would really differentiate the 13" from the MBA which I think it needs. It also needs to be closer to the 15" because currently you can pay a few $100 more and double your performance going from the 13 to the 15 - which is why every review said the 13" rMBP was pretty bad value for money. You can get an air far cheaper, or double your performance with a 15". The 13" is also the only laptop in the Apple line that would actually benefit from Iris pro as opposed to it being a downgrade from the current machines, so is the only one it makes sense to put it in.
Well said. Keeping the dream alive.
Iris Pro in 13", even BTO - sold.