Nope. I just updated my Ipad and my iphone and I didn't have to log out of any aps. It took like 3 hours to download the update, but I was able to multi-task while it was downloading. Def. plug in or it will kill your battery fast!
You have to close out of apps in the iOS 7 because there are some apps that still run continuously. Also, make sure that you sign out of any active app first before closing out so as to prevent your device from running slow.
When you single click on a running application - it moves to the non-visible bar below your screen - and is still running - and occupying memory - double click on the physical home button to make the bar visible - you'll see all apps still in memory - the new iOS 7 let's you multitask - like a regular computer - exchanging data between those running apps - but at the cost of draining battery power faster. The trick is to just keep running those apps you are using simultaneously and close unused apps.