Should I leave my current job, or wait for a promotion (cont'd)?

I started off at a new job 2 years ago working in a team of 4 plus 1 supervisor.

Over time I have been given additional responsibilities, taught new things etc. I am the sort of person who takes pride in my work and enjoys helping others to make their day easier. Go to work, do the job, get paid, go home, minimal fuss.

As time has gone by, my supervisor has all but given me his job. All he does is sits down and makes a thousand pointless phone calls, send irrelevant emails, eat as much food and trys sleeze on with the office girls. I cannot see how he justifies his job / salary. While I have never wanted his job, I just wish my supervisor would actually do some real work for once.

When he is away or on annual leave everyone relies on me to step up as 2IC (second in charge), something I am skilled and happy enough to pursue. All I have been getting is compliments on how extremely valuable and efficient I am performing both the supervisory job functions aswell as getting my own normal duties completed.

I have the support of every other employee in my own and other departments to knock this guy out of a job, my supervisor honestly cannot perform his own job anywhere near as good as I can do it. Best part of this is it has been noticed at a higher level (where it counts), I have been praised on my hard work and promised a promotion to his job (they want to give him another one) but he won’t take the other offer. The managers have said they can’t fire him (technically done nothing wrong by his employment contract) or force him into another job function as that’s the one he signed up for.

As my supervisor does nothing and I feel I have earned my place there, it’s starting to stress me out and I just can’t work as hard knowing that he is just sitting there doing nothing. When he is not there I can proudly say I love my job! Silly but true!

I want to get another job where I don’t have to put up with his lazyness, but don’t want to miss out on the promotion if it ever does come up.

Could someone please give me some advice on what to do?