Retirement or death are both sensitive issues. So is your fear of losing people who are important in your life. If you need to talk about this in your therapy, you should be able to. However, given the nature and sensitivity of the topic, it might be that your T himself has not come to terms with it ... I can't know the situation but it's a possibility. Have you ever brought up the issue with your other therapists? You seem to have a strong support network with your three therapists and, while it is much preferable to talk this out with your main T, if that can't be done right now you still can talk about it in therapy with someone else, work through it at least with yourself.