This may seem like an obvious thing, but I thought it wise to check. Can you please just confirm that when API V1 is turned off on June 28th that any existing apps which are still running against this API will fail gracefully.
So no crashes and no odd behaviour. I would expect it to work the same (to the user) as if there were on internet connection, so silent background failures. This is a question which applies to the iOS and Android SDKs.