Halving is definitely real, and people have already explained here what it's really about. However, halving might occur a bit off the schedule, I believe. More importantly, a thing that's not real and merely hypothetical but related to halving is that the price will go up. People have been talking about it for years, and many attribute the price boost of 2017 to halving of 2016, although I don't really see the connection. Anyway, while halving as a fact of reduction of the block reward is a real thing, its impact on mining, prices and adoption are debatable.