GSK has repeatedly stated they consider health care benefits for their employees a cornerstone. So it remains to be seen if they will jump ship. Even at that, a 30% figure could include a large number of very small companies, with not all that many employees. GSK operates globally. And executives are not going to give up their gold plated plans, so it is impossible to know if they can retain their executive plans but jettison the peons.
Retirement health care benefits may be at greater risk. But that would be regardless of health care reform.