From the You knew it was coming files:
If you haven’t started thinking about your Citrix StoreFront upgrade yet, consider this the start of your official countdown.
The End of Maintenance date will be December 17th 2014 when updates officially stop and then the End of Life date will be June 14th 2015. At that point there will be no more patches, upgrades or security hotfixes issued for the Web Interface 5.x product. 2015 is definitely a good distance in the future and 18 months should be plenty of time for a transition but depending on the level of customization you might have implemented on your current Web Interfaces, you should begin experimenting with StoreFront sooner rather than later. This will allow you to be properly prepared and have the right expectations when the inevitable crunch time comes.
Of course you could pony up the cash for the Extended Support to get you to 2020 but I can only speculate on what it will actually cost.