iOS 7.1 is now out, bearing mostly "minor improvements and bug-fixes", but also CarPlay support. At the moment there aren't any cars to support it, but as soon there are you'll be good to go. Well, if you're picking up a fancy new car anyway.
One of the main improvements is that Siri now works with the finger held down while on command, thus knowing the command is finished when the home button is released. Previously the voice assistant would wait for a couple of seconds of silence to know it was ready to jump to action. Both ways of using Siri will work with iOS 7.1.
Holders of iPhone 4 devices will have a quicker and smoother user experience downloading 7.1, as Apple has streamlined the interface for less powerful chipsets of the 4 and 4S.