If you're going to present an argument, at least have your facts correct.
The 13 inch retina macbook pro uses HD4000. The native resolution is 2560x1600. Specifications for you:
http://www.apple.com/macbook-pro/specs-retina/
Every ultra portable Apple product, except the 2799$ configuration of the macbook pro retina and 15 inch standard pro, uses HD4000. The 15 inch MBP uses the GT650M. I can tell you, that if intel matches or comes close to the 640M with the next gen ULV parts that Apple won't use discrete in the 2013 MBP. Already, nearly all of apple's products use HD4000. Now why would they use discrete when nearly all of their stuff (sans mac pro and imac) uses HD4000 _already_? They won't. Except perhaps in the high end configuration of the imac, which oddly enough costs nearly 3000$ - they would likely use a 780M for that (if they even release an imac this year, rumors indicate they won't.)
And I know you'll jump to the gaming argument. I've seen it here all too much - the thing is, the mass market doesn't care. Macbooks are not gaming machines, OSX isn't a good OS for gaming, and macs have never been designed for gaming. Period. So don't bother citing gaming performance of the 650M. Apple merely wants a display processor that can make the UI and experience snappy - apparently they thought it (HD4000) wasn't enough for 2880x1880. But this will change with Haswell.