Here's what I found. Solution that worked for me is not intuitive due to the app upgrade user interface. I had 3 apps hung in "waiting" state.
1. Go to the App Store and select the "purchased" tab
2. Select one of the waiting hung apps - a pop up window opens for the app selected
3. In the app pop up window for the app it will show the update progress status circle frozen just like it shows on the "update" tab screen.
4. Here is the part that is not obvious due to the user interface!: Tap the update progress circle that is frozen!!!!!
5. Progress circle changes back to "update" button
6. Tap the "update" button
7. App update will restart (and hopefully complete :-) )
8. At update completion the button changes to "Open"
9. Open and verify the app works
10. Repeat for other hung apps
Not sure but suspect that you can search for app instead of using the purchased tab in step 1 and start the pop up that ways as well.