Do consumer high temperature RF ASICS exist at 200C?
They do (At least for some ASIC components) -- some of them leverage Silicon-On-Insulator technology to help achieve those high temperature ratings. X-Rel for example manufactures many "common" analog / etc components that can hit 230C+ temperatures.

They don't make anything RF at the moment, but I'd be curious to see if Peregrine's SOI process is similarly tolerant of extremely high temperatures.