I don't think it's possible. If he has a deep run, he's going to get a 50m/avg contract from someone - Giants, Raiders, Steelers, Jets(HA!), Browns, Rams (really good fit), and others need a QB. We've gotten out of salary cap hell and drafted our QB of the future in McCarthy who will be a lot cheaper, allowing the team to build around him and make upgrades. I don't think the team can deviate from those plans.
I also, personally, think McCarthy is going to be a very good QB in KOC's system.