I'm working with a company that has a couple of apps on the app store. They are concerned that with this April 2020 requirement that their apps will be non-functional or removed from the app store unless we update using the new SDK and requirements. We have the apps working on all iOS 13 devices, and have no updates to currently apply to them. Do we *need* to update using the new iOS 13 SDK or are the apps okay to exist without updates?