Deadlines can be moved. Resources can be allocated to projects to account for unforeseen events. Penalty payments can be paid. It's definitely not ideal but often established businesses can cope with someone leaving unexpectedly. It can kill a startup, but so can most things.
What I'm saying is that you shouldn't be too surprised if a threat to leave is met with "Oh. That's a shame, but nevermind. Bye." You may feel you have a great deal of power over your employer because you see your role as important or even critical to the business, but they might see your role very differently.
Usually because your employer has no idea how important you are to the effort. Often employees have regard for developers based on fame or project they've done before. Rarely on skill or how important they are to current efforts. When asked who were the most important developers to our OS group, the engineering manager named the original team that created the project. He got a perfect score - completely wrong. They had all moved on and the current OS team were young folks, new hires and recent additions. Including me at the time.
Be very diligent about communicating! You can easily get forgotten in a larger effort.
Deadlines can be moved. Resources can be allocated to projects to account for unforeseen events. Penalty payments can be paid. It's definitely not ideal but often established businesses can cope with someone leaving unexpectedly. It can kill a startup, but so can most things.
What I'm saying is that you shouldn't be too surprised if a threat to leave is met with "Oh. That's a shame, but nevermind. Bye." You may feel you have a great deal of power over your employer because you see your role as important or even critical to the business, but they might see your role very differently.