No one knows when Android L will be available for everyone, it could be months, even a year or two. Most probably it will be coming later this year.
If you want to get a taste of the new version of Android, Google have released the new Android L keyboard on the Play Store, free to download. Even though the keyboard itself doesn't have any major updates, it's great seeing a fresh new design.
If you want the full Android L experience, you could even go as far as installing it on a Nexus 5 or Nexus 7 - How to install Android L on Nexus 5 or Nexus 7