Asking faculty up for tenure about the tenure decision
Getting tenure is a major life event for faculty. So the same rules apply that also apply for questions that revolve around "how is your unborn child doing", "how is your parents' health", "has your spouse recovered from that recent illness": these are kind questions to ask a human, and if the answer is positive, you get all of the credit. But if the answer is negative (tenure denied, parent died, child is born with a disability), it puts a rather serious damper on a conversation.

There is no good way to describe whether the question is appropriate. In the end, these are personal questions that relate to family and, in this case, career aspirations. Whether or not you are in a position to ask the question depends on how well you know the person, and whether you have a relationship good enough to have conversations about awkward and difficult topics.