iOS 7 is unlikely to run better on the iPhone 4 than it does in iOS 7.1



From OSNews:

If you're sticking with the iPhone 4 for another year, iOS 7.1 makes performance tolerable enough that using the phone isn't unbearable.

Good news for iPhone 4 owners - and good on Apple for taking care of this demographic.

  iOS 7.1 on the iPhone 4: as good as its going to get