According to a recent report from TrendForce (via MacRumors), those updates are scheduled for the end of Q3 2018 which will either be in September or October. Apple typically hosts its iPhone events in September and generally speaking they try not to mix its Mac and iPhone announcements together.
Sometimes Apple does host an event in October in which new iPads are announced, and it is possible that the event could be where the refreshed 12-inch MacBooks and MacBook Airs could be announced as well. TrendForce’s report does not mention the 12-inch MacBook, but presumably it will be refreshed as well considering that it has been about 1.5 years since the laptop was updated.
In any case if the analysis is correct, we should have the details in the coming months, so if you don’t need a new laptop at the moment, it might be a good idea to hold out to get the latest models.