GaN will play a strong role in advanced RF and microwave applications including 5G and satellite communications. The specifications of these systems will push next-gen GaN devices towards mm-wave operation. The challenges and opportunities for commercial deployment of GaN are identified and a variety of circuit designs are presented. A 5G high-linearity power amplifier MMIC in 0.20um GaN with Pout=36dBm at 51.1% PAE and a Sat-com Ku-band mixer in 0.25um GaN with conversion loss < 10.5dB and IIP3=36.4dBm are demonstrated.