I'm also experiencing the same thing. I did every possible ways to have this problem fixed, but nothing seems to work out. I have all in all five apps waiting and I'm afraid the number of apps needed to be updated are gradually increasing.
By the way, I'm using an iPod Touch 4th gen now, not an iPhone.
P.S. I solved the problem now and I'm only left with "installing..." status. Here's how got rid of that "waiting..." status:
1) Open iTunes with your device connected to the laptop or pc.
2) On the left sidebar, press "Apps".
3) Then on the lower right, you'll see like in my case, "30 (this varies on the number of apps available for updates) Updates Available".
4) Click on the desired app you want to update.
5) Lastly, after updating, press the "sync" button.
It worked, though my apps are currently stuck on "installing..." status. I don't know if this'll work in your case, but there's no harm in trying the procedure, right?