Dallas is in all kinds of cap trouble; so they will have to do something. Trading Robertson to fix that problem seems like a terrible idea - but he is RFA after this year, and a UFA one year after that - so he will be commanding a very hefty raise. He makes 7.7 now, which is a steal - but given his production, I'd expect he will be in the 10+ range. If this offseason gets too crazy, with Ehlers, Bennett and Boeser getting close to 10, then Robertson will be in the 12+ range.
So, you could see a scenario where Dallas decides to address their cap problem by dealing Roberston, but that would mean not taking equivalent salary back.