According to the sources, Best Buy will begin stocking AirPower by the end of March. Because the store is an authorized Apple reseller, it often receives units around the same time as Apple's own stores. Neither report has a specific release date.
Apple announced AirPower, which can charge an Apple Watch, AirPods and iPhone simultaneously, last year at an event alongside the Apple Watch Series 3 and iPhones 8, 8 Plus and X, all of which support wireless charging. AirPods will require a special wireless charging case. The AirPower mat and devices will communicate with each other, deciding which items need priority and in what order.
Last year, an independent Polish retailer started showing AirPower online for roughly $199, but that's most likely just a guess, as there's no reason to imagine that one store would know (and that Apple would let that slip stay online so long). We also don't know the pricing and release date of the case that the AirPods will need to charge.
But with a bunch of Apple rumors all picking up steam at once, including new iPads (also rumored for March), second-generation AirPods and now the AirPower, it sounds like it may soon be time for another Apple event in Cupertino.