Application update, what will be the release date in appstore
Nowadays, apps submitted to the App Store will take 6 to 8 days to be reviewed based on how many apps are queued for review.

If your application is showing the status Waiting for Review, it means your app is not yet reviewed by Apple. Once the review process has started, your app will show the status  Under Review.

Updates and new releases follow the same rules.

You can also refer here.