Will legacy watchOS 1 apps continue to run as before?

I have a watchOS 1 app with a large user deployment that makes extensive use of App Groups in the WatchKit extension. Will the app continue to run as before in some kind of "legacy mode" even when a device is updated to watchOS 2? Or is it imperative to migrate the app to the new model to keep it operational?

Current WatchKit apps should run without any changes.

That contradicts the Apple documentation, which clearly states that apps that make use of App Groups will have to be rearchitected.

Will legacy watchOS 1 apps continue to run as before?
 
 
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