THe money will go somewhere. IF the company doesn’t increase their pay to the employee, the company will have the money to re-invest and grow. Or they will pay it out as dividends to their shareholders.
That's entirely true, and a far more likely scenario than the company passing the FICA tax savings on to the employee. It is, after all, an expense to the company so it makes sense for the company to use the savings to the best advantage of the company itself. So if we can agree that the odds are heavily against the employee getting the money then can we also agree that it should not be factored into the employee tax bill under the current tax law?