[greenyoda]

People leave their jobs all the time, for all different kinds of reasons. Dealing with that is part of management's job. It's not your problem.

Also, the company has no obligation to you. They could fire you a day after giving you your big raise if they were suddenly short on money, or if they decided to cancel the product you were working on, or if they just felt like it. Why should you have a commitment to them that they don't have to you?