It certainly doesn't sound as catchy, however, AMD believes it to be the name that will take its increasingly 'heterogeneous' Fusion System Architecture into the future, that is the newly named, 'Heterogeneous Systems Architecture'.
FSA is an architecture built upon open standards such as Open CL and and C++ AMP, that attempts to close the programming gap formed between the CPU and the GPU. The standard focuses on reducing latency and the need to copy data between the CPU and the GPU in order to perform specialised operations, enabled through hardware support with a unified memory controller and hardware acceleration of task queuing.
Why the name change now? AMD's newly released Radeon HD 77xx - 79xx series of graphics cards feature AMD's new GCN, Graphics Core Next architecture, which supports some of the hardware features needed to make the firm's FSA a reality. AMD is being a little sketchy at this stage as to just how far developers will be able to go, armed with HSA and GCN, however more details are expected to emerge in the near future, so stay tuned.