Apple will be commencing its annual iTunes Connect shutdown on Saturday, December 21st this year. The shutdown will run until Friday, December 27th. During this time developers will not be able to submit app updates or price changes in the iOS and Mac App Stores. Apple announced the dates for this year's holiday shutdown in an email to developers late last week:
iTunes Connect will be temporarily unavailable from Saturday, December 21, to Friday, December 27, 2013.
During that time, iTunes Connect will not be accessible and you will not be able to submit any apps or In-App Purchases. Processing of any Newsstand Atom feeds will be delayed until after December 27. Sales and Trends reports via the Autoingestion tool will be available but may also be delayed.
Also, you should not schedule any pricing changes or apps to go live between those dates. Pricing changes scheduled to take effect in that date range will cause the app to become unavailable for purchase until after December 27. Similarly, apps scheduled to go live during that range will not be released until after December 27.
If you have any additional questions, use the Contact Us module on iTunes Connect.
For end users, the shutdown won't have any noticeable impact with the exception of no new apps, updates, or price changes appearing during that time. All other download and upgrading functions will continue to work as normal.