Anything's possible, including that.
My mother spent my entire childhood threatening to do all manner of unthinkable things, ranging from self-termination, to leaving home, to putting my brother and me into a home for troubled children. She never did any of those things. She simply couldn't cope and wallowed in self-pity.
Perhaps your mother is simply doing that -- crying out for attention, or help. Perhaps she means it and she's trying to prepare you for her departure.
From the nature of your question, though, it sounds as though she's just venting. Don't worry about it. It may never happen.