Today, an AnandTech article states (or rather, implies) that Nvidia has discontinued the 750M which is used in the current MacBook Pros:
"With the launch of the new GTX 970M and GTX 980M, it's also worth mentioning that NVIDIA is officially discontinuing some of the existing mobile parts. The current lineup of mobile GPUs from NVIDIA now consists of GeForce 820M, 830M, and 840M for the casual/less demanding market. The 820M is actually a Fermi-derived part, while 830M and 840M use GM108 with 256 and 384 cores, respectively. At the top of the product stack, the GTX 980M and 970M replace the GTX 880M and 870M, while GTX 860M and 850M continue as the "mainstream gaming" notebook GPUs; 860M also continues to be offered in two variants, a Maxwell GM107 version and a Kepler GK104 version, though the latter hasn't been widely used."
http://anandtech.com/print/8585/nvidia-geforce-gtx-980m-970m-mobile-maxwell-gm204
If this is true, then Apple either has to rev the MacBook Pros soon, or they've stockpiled quantities of an outdated GPU so they can continue to build lackluster graphics into their Pro laptops for months to come. I wouldn't be surprised if it's the latter.
The 750M GPU in the current machines has almost identical performance to the 650M that was introduced in the very first 2012 Retina models.
http://barefeats.com/rmbp14.html
And here we are, going into 2015...