Hello Maria,
Ettus, and a few other sources, supply FPGA based GNU Radio blocks, but they do not support the B210. The more fundamental issue though is that the AD9361 has a maximum sample rate of 61.44 MS/s, so FPGA acceleration will not help in increasing the rate above that maximum. If your application needs a higher rate then you'll have to look at a different radio.
Ah, Marcus has replied saying much the same things as I've been writing. You can find out more about the FPGA based architecture that is available on the larger Ettus radios at the links below, including GNU Radio integration.