iOS 7 utilizes Multipath TCP to make sure you're always connected when you want to be

It appears that iOS 7 includes some new networking capabilities, with Multipath TCP now part of how iOS devices connect to networks. Multipath TCP allows a device to maintain multiple connections, like Wi-Fi and cellular, so that if one connection is lost, the other immediately takes up the slack. A download started over Wi-Fi could continue over an LTE connection if the Wi-Fi connection was lost, says 9to5Mac:

With MCTCP your iOS 7 device will be able to stay connected over both LTE and Wi-Fi at once. If your Wi-Fi connection fails, the LTE connection would continue downloading the data uninterrupted. You would likely never even know the difference unless you tapped the screen and checked your signal indicator.

So if you're downloading, for instance, a few app updates and you lose Wi-Fi, your apps should still update just fine if your connected to your cellular network. iOS 7 is the first piece of consumer software to utilize MPTCP. Since it does not require new hardware, MPTCP can be utilized on any device running iOS 7.

Source: Olivier Bonaventure, via 9to5Mac