Coprocessors are something I vaguely remember from the era before the first Intel Pentium processor, but it's possible that they will soon arrive again for new Intel Xeon processors. Both Xilinx and Altera showed off their FPGA coprocessors at the IDF last week:
Essentially, the devices plug "directly into the processor socket of dual- or quad-socket servers" in order to provide "high performance application acceleration ranging from 10x to 100x compared to processors alone, while simultaneously reducing overall system power consumption." The modules act as targeted CPUs, effectively computing very specific tasks in a much more efficient fashion than a general microprocessor can alone, which could boost the speed of scientific, financial, and life science applications that rely on very particular calculations.
Of course, mainstream adoption still has quite a ways to go, but the quicker we get dedicated physics and AI coprocessors to go along with these snazzy new GPUs, the happier (and poorer) we'll be.