This seems like a pretty empty threat. The government already has the authority to demand lawful access. "Lawful" includes a warrant. If the government wants to show up with a warrant, I expect companies to aid the government in gaining access to legally-relevant data. If they want help in a broad-spectrum fishing expedition, the US at least has no clear affirmative authority and a small pile of legal precedent based upon the Fourth Amendment that says they in fact lack that authority.
The fact they had the technological capability previously to act without Constitutional authority is irrelevant. Show up with a warrant or go pound sand.
Whether they get a warrant or not is orthogonal to the question of whether they ultimately succeed in breaking security for virtually everyone and everything.
In other words this notion of “get a warrant or pound sand” ignores that even with a robust legal warrant-requiring regime, they still would need to require back doors (key escrow, effectively the same thing) that would screw up security royally in order to get what they want.
The fact they had the technological capability previously to act without Constitutional authority is irrelevant. Show up with a warrant or go pound sand.