According to our sources, AMD is studying the x86+FPGA+HBM2 combo on an 2.5D Interposer, to realize a Semi-Custom chip developed for an unknown customer.
As we can see in the following scheme, AMD could use a FPGA to improve the effectiveness of its CPUs, like Intel will do thanks to the acquisition of Altera (Xeon with integrated FPGA).
Some months ago we became informed about two AMD big wins, and this study could be correlated to this rumor. Microsoft is testing the use of FPGAs in its own server (Project Catapult), and other giant companies (Facebook, Google, etc.) are studying the FPGA implementation, too.
We don't know if this AMD studies are correlated to these rumors, but one thing is definite: AMD is keeping the doors open to all opportunities.