I'm having the exact same problem on my iPhone 5s, iPad mini (both are jailbroken) and on a non-jailbroken iPad4. The Update All is not clickable (like there are no actual updates) and when I click on the individual app update button it opens the app instead of updating them. This started yesterday afternoon for me. The iPhone and iPad mini are on 7.0.4 and 7.0.6 respectively and the iPad 4 is on 7.0.
Note, we have two iPhone 6's running 8.0.2 and they update fine. It's not a space issue and restrictions are not applied (if either are your case then try fixing those first.)
I've tried the following to no avail:
Manually close the App Store and reopen.
Attempt update over LTE rather than WiFi.
Reset (hold home and power button until powered off.)
Sign Out Apple ID and sign back in.
Sign Out Apple ID, reboot and sign back in.
Reboot my router.
Reboot my modem.
Sacrifice a live chicken (no, not really.)
What actually works but doesn't seem to make a lot of sense...
Search for the app that needs to be updated and open the description. Press Update which prompts you for your App Store password... for each app... then that individual app updates (not so bad with Touch ID but still a bit strange.) Not too tough a work around and works until we figure out what's going on unless you have a lot of updates.
It seems to me that more and more people are having this issue which just started up yesterday or Friday. Since it's not just me and it's happening to jailbroken and non-jailbroken devices it appears that the problem is with the App Store and not us... or... randomly affecting certain folks, locations or iOS versions.
I removed all the apps that said UPDATE. I then logged out of the App Store, then did a Hard Reset. I then logged back into the App Store, I downloaded YouTube, for example and when it finished installing it still said UPDATE?
Oh, and now some apps still show the the cloud with arrow(download) even though the app is already installed.
Yeah... this is apparently only hitting a small portion of people or we'd be hearing a lot more static. Seems like for those select few perhaps upgrading to iOS 8 may be the only course of action. Not a pleasant choice for jailbreakers but let's see what happens when iOS 8.1 is released on Monday.
When I noticed the issue, I thought about the fact that even if you called or went to the genius bar, they would at the least tell you to restore the OS or upgrade. I am jailbroken and would prefer not to do that, though I have considered just saying screw it and going to iOS 8.1 since I have an iPhone 6 now. I will miss a few tweaks but the asinine 9 icon folder view on the iPad is probably my biggest issue with it at this point. At least they have the scrolling view now which is something and I would get the benefits of iOS 8 with iCloud Drive, Continuity, etc.
SO, I tried to sync to iTunes on my Mac Mini to see if it would do anything and it does not upgrade the Apps. It seems to hang up on preparing apps for sync and then eventually just moves on to the next step without updating them.
So, I set the iPad to automatically install updates and it seems to be updating them now. The updates still have the word Update beside them in the list and it is not showing the version number, but the few apps that mention the version number in the comments and that also have a way to check the version number seem to match.
I don't; really love the idea of auto updates as I usually let them sit for a couple of days to see if anything blows up, but it gives me a way to at least get updates until they get the 8.1 Jailbreak to a workable state.