Google has updated almost the entire inventory of its native apps for Android 4.4 just before the release of Nexus 5. And more recently, we have seen it release new versions of Hangouts and Google Keyboard.
Now, you can download the latest version of Play Store running on Nexus 5, on Android 4.4. Kit Kat. This version is an upgraded version (Play Store 4.4.22) of the Play Store app that Nexus 5 was shipped with (Play Store 4.4.21). The upgrade features certain bug fixes, new navigation and a few performance upgrades.