Update: (October 3, 2014) Citrix came out with an update for Receiver their iOS app. Some minimal testing shows that it is working with iOS 8.
Non-action Required: If you use Citrix Receiver on your iPad or iPhone do not upgrade to iOS 8 until further notice.
Description: According to Citrix’s website, their software is not compatible with iOS8 at this time. Their current estimate on an updated software is early October.