How does the upgrade process work?

I have the existing Hue Bridge and would like to upgrade to this one. How does the upgrade process work? Do I need to bring the old one to an Apple Store to purchase the new one? The new Bridge never seems to be available online which suggests there's some kind of catch to getting it at the reduced upgrade price. Please explain.

Philips HUE HomeKit Upgrade Bridge (for Current HUE Bridge Users)

Philips HUE HomeKit Upgrade Bridge (for Current HUE Bridge Users)

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