Word is going around that AMD is going to switch to GlobalFoundries' 28nm SHP (Super-High-Performance) node in 2015 for upcoming GPUs. This process promises lower voltages, which promises to give greater room for higher clockspeeds on AMD's new GPUs.
The company won't entirely abandon TSMC though, the next-gen "Zen" CPUs will reportedly be made on TSMC's 16nm FinFET process. Zen is the successor to the Bulldozer architecture.
AMD's GPUs in 2015 could be based on its latest Graphics CoreNext 1.2 architecture, and AMD needs every means to minimize voltages, and crank up clock speeds.
The company hasn't abandoned TSMC completely just yet, with reports speaking of AMD using the Taiwanese fab's 16 nm FinFet node to manufacture its next-generation "Zen" CPUs. Zen is the successor to AMD's "Bulldozer" architecture and its derivatives ("Piledriver" and "Steamroller.") It could feature a radically different core design.