Without new product, they will be left with expired patents and competition with generics. Period.
I don't suggest corporations are altruistic. I suggest they're practical.
To stop doing R&D is to cut off their nose to spite their face. New drugs are their most valuable and profitable product, one which means life and death in many cases. They aren't going to close down the process by which it's produced.
They will find another way to recoup losses and turn a profit.
But they will restrict their contracts with those who undercut their other markets...