In short there should be no separate "hypothetical tag," but if we are serious about addressing political issues, then simple forecasting is a major part of that. In fact, this strikes at the core of a question which I asked previously, which is about increasing the Political Science on this board.
Forecasting is a basic function of Political Science. If you look at this quarter's edition of the American Political Science Review (APSR, the flagship journal of Political Science), no fewer than five titles are explicitly predictive! It is true that some people argue that Political Science is bad at predicting things, but within the discipline itself, it remains an open question and many argue that in fact, we're pretty good at it. The accuracy of the predictions is immaterial about whether or not this is a core facet of Political Science, and even social science generally, which it is.
There have been noted failures, such as the inability to predict the success of Donald Trump, but there have been a number of successes as well. Directly related to the question which spawned this answer, which is international security related, John Mearsheimer predicted with uncanny accuracy the outcome of the Gulf War. Again in 2002, most leading experts were absolutely correct in assessing when and how the invasion of Iraq would go.
This is not an invitation for WAGing, but instead is an argument that people should be able to make answers, with well considered historical facts, trends and theories of behavior to back them up. There will likely have to be a lively discussion about what is actually reasonably possible to forecast, given available information, and many answers will have to be policed for quality. Frankly, it will be difficult for people who are not professionals to do correctly, at least up front, but it will be possible. Allowing these kinds of questions is important, however, because preventing even reasonable forecasting means that the most interesting questions of politics are unanswerable, and essentially this is a dead site walking.
In some ways, this is just a matter of "style" but style is important in this case. As was shown in the terrorism question, you could reasonably recast the question into one which is about factual history, but that is an inferior question for three reasons: First, that question is not likely to attract searches on that topic from search engines, or even on SE at large because the title is focused on historical analysis. Second, it hides the motivating issue in the body of the question, making the overall question much more dull.
Finally, and in my opinion most importantly, forcing questions to be recast in that was is imposing a way of communicating about political issues that is foreign to popular, professional and academic discussion. When asking about what would happen in the future, people are not expecting a crystal ball prediction, but a reading of what has happened in the past and a reasonable extrapolation from there on what is likely although not guaranteed to happen. No one, anywhere, ever was thinking to themselves about terrorism at the EURO, and then said in their mind "I wonder how past high-profile events have dealt with terror attacks" unless forced to. SE's advantage in every thriving stack is that it allows casual users and novices to communicate easily with experts, and forcing everyone to use verbiage they would never use to convey their meaning establishes a barrier to usage which makes the site less valuable.
In the end, there does need to be a robust discussion surrounding what are acceptable predictions here on this site. Furthermore, norms need to arise regarding the theoretical assumptions and empirical statements that should surround predictions. This all needs to take place in another question. Nonetheless, this is a basic feature of Political Science, and is a dire need which politics.SE can and should fill.