https://www.techradar.com/news/delayed-macbook-delivery-dates-could-point-to-a-wwdc-2018-refresh

Apple holds its Worldwide Developers Conference every year, and with WWDC 2018 kicking off on June 4, there's plenty of speculation about what Apple might have in store for iOS, macOS, tvOS and watchOS. It turns out we might just get some new hardware too.

As Apple-centric sites including AppleInsider and The Mac Observer have noted, some MacBook and MacBook Pro models are now displaying delivery dates after WWDC 2018 starts – suggesting Apple is about to refresh at least some of the models, and doesn't want to deliver hardware that'll soon be out of date.