Hmm according to the "leaked" specs, we're getting both the Iris Pro AND the 750M, which I'm extremely happy about (since it's the best of both worlds since the Iris Pro will be better at Photoshop/OpenCL) but think that it's overkill so maybe it's not true. Then again if Apple does something suspicious, it's probably for a good reason.
Iris Pro + 750M + 16 GB RAM + 512 GB SSD sounds like a good, but very expensive upgrade if the current prices are any indication.