Just like last December, Apple will be shutting down iTunes Connect from December 22nd to 29th for the winter holidays. While this service is shut down, registered Apple developers will not be able to manage their App Store content. This means that there will be no updates, price changes, releases, and other changes on the App Store between Dec. 22nd and 29th.
While these back-end App Store services will be shut down, the store itself will remain open for business per usual. The only apps that will be unavailable for purchase are ones that have a price change scheduled between the dates that iTunes Connect is not running.