Microsoft Dynamics GP 2015 was released December 1, 2014. Here is a quick list of all the resources you need for this exciting version:
Microsoft Dynamics GP 2015 System Requirements 
What’s New in Microsoft Dynamics GP 2015 PDF
What’s New in Microsoft Dynamics GP 2015 R2 PDF
Microsoft Dynamics GP 2015 Functionality Guide
Features Since Microsoft Dynamics GP 2013
Microsoft Dynamics GP 2015 Blog Posts
Microsoft Dynamics GP 2015 R2 Blog Posts
See what is new since Microsoft Dynamics GP 2013
Ready to evaluate Microsoft Dynamics GP?