There was a rumor that I saw somewhere a month ago that Nvidia in 2014 will have a technology that makes use of Unified virtual memory named Maxwell. Should end up in the GeForce GTX 800 series coming out next year.
Next two GPUs from us: Maxwell is coming with unified virtual memory, which makes it possible for GPU operations to see the CPU memory and vice versa, so program-ability is easier. After that is Volta, which is even more energy efficient, which has a new technology called stacked DRAM.
Volta with Stacked DRAM, will have a bandwidth of 1 TB/s. This a completely new approach to the way memory is used by the GPU.
Volta is going to solve one of the biggest challenges facing GPUs today, which is access to memory bandwidth. With Volta, we’ll prevent from getting off our chip onto a PC board – it will have DRAM on same silica sub-strate, which will carry a whole bunch of DRAMs stacked atop each other. We’ll cut a hole through the silicon and connect each layer. We’re going to achieve one terabyte per second of bandwidth.
Volta would probably be used with GeForce 1000 series, considering Maxwell will be used for at least next two generations.
There's also a rumor that says since this technology is getting more advanced and better Nvidia might have graphic cards by 2014 that can get up to 6GB DDR5 RAM even possibly 8GB DDR5 RAM and by 2016 your looking at 10GB DDR5 RAM up to 14GB DDR5 RAM. Take it with a pinch of salt this part is a rumor.