I would agree that you should not mention it in your review. Until you have an alternative plan which is confirmed, then you should still not mention it to the company (your colleagues are different). But can you not look on this as an opportunity? You have not mentioned who your new boss will be, is it her boss, or will someone else be coming in? If it is her boss, then it may be time to make friends and influence people, as they say. By communicating whith him/her more and pressing opportunities and change, you could perhaps find yourself gaining a better standing within the company - it sounds as though it will be a better environment anyway while your boss on leave. Of course that will depend on your new boss and the organisation, and if you cannot see a change happening even with your boss away then you have to continue with your plan to leave, just be aware that there are lots of bad mangers out there in other companies too.
