i think you should leave the situation as it is for now. wait it out to see what will happen. sooner or later you will know whether is he gay or not. cheers:)
i am glad you can take this positively and not be like a vengeful person who wants to break them up (one up to you:D) don't worry, i am sure your the other half is there waiting for you to find him:)
There are a lot of cases about how teacher and student having relationship, and usually the teacher ends up being the one that lose out more, so for the benefit of him, dun do anything:D