While it could pose a temporary dip in the quantities of electronics being sold/manufactured, you can bet the big electronics manufacturers aren't going to sit on their hands and hope that China opens up more mines to sustain the global electronics market. I've got a feeling that this could very well spur some new development in an area that dramatically affects sustainability: PCBs (printed circuit boards). In a typical electronic product, 95% of its environmental impact is a result of its PCB and various electronic components (all of which are made using toxic rare earth elements). This leaves a sad 5% for the housing, the area in which most 'green' products focus on.
If global supplies of these crucial materials are dwindling, it will demand new research into alternate (hopefully greener) technologies to drive the ever-growing electronics market.
Here's to hoping!