Unlike launching a new architecture into the high-end segment, NVIDIA is set to release the followup to Kepler called Maxwell in the mainstream space in the current Series 700 lineup, it in fact it is going to be the GeForce GTX 750 Ti. SweClockers report that the first Maxwell GPU would be the GM107to be released February 18th of 2014. The 750 Ti will replace the GeForce 650 Ti. 

There are no specs available, but Maxwell will get a special buffer for the CPU and GPU. We also know that it will get Unified Virtual Memory as such the GPU and CPU can share memory. 

We expect higher end Maxwell based cards later this year, and though we do not know for sure, they might have a special integrated 64-bit ARM processors say a NVIDIA Maxwell GM117 with a Denver dual core ? Then again, for mainstream and high-end that would not make much sense. Entry level however would. Ah well, we'll see.

As always this info is speculation.

First NVIDIA Maxwell GPU-Based Graphics Card is the GeForce GTX 750 Ti