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.

If I know a faculty member is up for tenure this year, is it appropriate to ask them for news about the tenure decision?

No.

It’s completely understandable that you are curious and want to know, and I’m pretty sure your desire to ask is motivated by noble feelings of sympathy and care for a fellow human being you interact with professionally. At the same time, this is a question that for many academics is very fraught and anxiety-producing. We are talking about a single binary bit into which 7-8 years of hard work and emotional self-investment are being channeled. A negative outcome can very possibly have career- and ego-crushing consequences for the person in question. Do you start to see why the value of that bit might be something that some people (especially people who are insecure and/or who have less than full confidence about the outcome) do not wish to discuss or be asked about? As Wolfgang said in his answer, you might get lucky and the discussion will go well, but it’s also possible that it will go disastrously wrong, or, more likely, it will just be a tense and awkward moment.

To summarize: It’s none of your business. Don’t discuss it unless: 1. the faculty member brings it up first, or 2. you heard from a reliable source that the person got tenure and wish to congratulate them.