Is it required to use XCode v5 to host an IOS Mobile App in itunesconnect.com?
Yes. On January, Apple, sent and email to the Developers stating that:


  Starting February 1, new apps and app updates submitted to the App Store must be built with Xcode 5 and iOS 7 SDK.


This can be found, too, in the iOS7 developer's page, were it's added:


  Use Xcode 5 with iOS 7 SDK to compile, validate, and submit release versions of your iOS 7 apps to iTunes Connect.