Sale AirPower can begin after WWDC 2018
Interestingly, while there is no exact information about the release date of AirPower — some insiders say that Apple will announce the start of sales
Simultaneously with the release of AirPower in what's the case for AirPods with support for wireless charging. About the plans to release this for Apple also spoke at the presentation in September 2017. Wireless hard case for AirPods will be included in a set of headphones, but if desired it can be ordered separately. The price is not yet known, but it hardly makes sense to expect it to be low.