If you're buying a Nexus 6 or Nexus 9, you can get Android Lollipop from November 3rd. But if you already have a Nexus 5, 7 or 10, you should get it in a free over-the-air update in the "coming weeks" according to Google's blog. Of course, if you want to, you can try the beta version now by following our guide: How to get Android L now.