Zeroth approximation: even the experts don't know, I am not an expert, so I know even less, thus I should not make any of my decisions based on singularity-related arguments.

First approximation: find a reference class of predictions that were supposed to come true within 50 years or so, unchanged for decades, and see when (some of them) are resolved. This does not require an AI expert, but rather a historian of sorts. I am not one, and the only obvious predictions in this class are the Rapture/2nd coming and other religious end-of-the-world scares. Another standard example is the proverbial flying car. I'm sure there ought to be more examples, some of them are technological predictions that actually came true. Maybe someone here can suggest a few. Until then, I'm stuck with the zeroth approximation.