So with Maxwell coming over the horizon, Nvidia have announced the step after it to be codenamed Volta.
Seems like this will be a much bigger step than Unified Virtual Memory on the upcoming Maxwell GPUs, since while UVM will open up both CPU and GPU memory, Volta's memory bandwidth will be a huge leap ahead. I paraphrase Nvidia CEO Jen-Hsun Huang's comments about memory limitations at the moment: Need more bandwidth.
Source:Engadget
Roadmap:
Source:The Register