Alright, there's only one thing you can try at this point to see if it revives the iPad and this will depend on where it stopped during the upgrade.
Disconnect the device from it's cord, if plugged in.
Press and hold your Sleep/Wake button (on the top) and Home button (on the front) together for around 10 seconds.
When the Apple logo appears, release both buttons.
The next thing you should see after the Apple logo is the home screen a few minutes later.
If, however, it returns to the "Connect to iTunes" screen then the operating system is damaged and a restore must be done. At the end of the restore, you should be able to recover from your iCloud backup however.
Also, there is a slight change due to the way the iPad crashed that a normal restore may not work. If that is the case, then try the following;
The following procedure is a special firmware recovery mode (DFU). It will erase your Apple device, re-install the operating system, and then re-sync user data once it is done (provided you have a backup of some kind).
Make sure you have downloaded and installed the latest version of iTunes on your computer before attempting this:http://www.apple.com/itunes/download/
(Mac users can run System Preferences > Software Update (or “Apple Store” for OS X 10.9 users) > Check now to get the latest version for their system in most cases.)
* Open iTunes on your computer and connect the Apple device directly to it
* Turn off the Apple device (press the sleep/wake button on the top until the device completely shuts off, not just screen sleep).
* Hold down the sleep/wake button (on the top) AND the home button (on the front) for 10 seconds
* Release the sleep/wake button but CONTINUE to hold the home button, until...
* iTunes should pop up and tell you it’s found a device in recovery mode, click OK and continue along for the restore.
Note: When you are in DFU mode the device's screen will be completely black.
Note #2: it may ask whether you wish to restore a backup from iTunes or from iCloud. You should use iCloud in this case as you indicated previously.If you still have concerns, please do not negatively rate my answer, simply reply back before rating. I'll be more than happy to work with you further
. Hopefully, this info will answer your question. When you are satisfied, please give my answers a positive rating. You are judging my personal service only (not this website, the price, or your issue) and high ratings assure I remain in good standing.
Thanks and good luck,