When submitting a new app, you can specify a future date for its availability. For exemple, you can set in March your app to be on the store on Christmas. But I've read in some forums that if your set that availability date in the future for an update, the app disapears from the store.
Is that right ?
If yes, is it possible to send an update for validation and set a future date for its availability, without loosing the current app that is on the store ?
Yes, you can submit an update but ask Apple to hold it after approval until you release it (it's an option in iTunes connect), thus keeping an old version on the App Store and allowing you to choose exactly when the update is released.