You’re unlikely to get fired during this merger. Firing is only done for cause, for either behavioral, performance, or legal problems. In many companies, you’d also be first put into a Performance Improvement Plan, where the problems that might lead to you being fired are formally raised to you and you’re given the conditions you need to meet to not be fired.

What you’re likely facing is a layoff, where a company terminates your job because your role is no longer needed. This is important, because in a layoff, you get severance pay, unemployment insurance, and potentially other benefits, while being fired may impact your ability to get these benefits.

Generally, it’s better to not quit if you don’t have to. If you stay and you get fired/laid off, you lose income you were about to lose anyway. If you quit but could have stayed and kept your role, you lose income you didn’t have to lose.