He's talking about germanium channel FinFETs, GaAs was intended to entirely replace silicon, which probably was never going to happen.
GaAs logic is probably happening at some point, just not yet. All improvements like that which would be incredibly expensive to develop will be held off on until all cheaper options have been exhausted. It does seem to be slowly moving though.
GaAs is gallium arsenide, which still has applications in high frequency transistors.