The development team has posted a more detailed explanation
regarding beta clients versus launch client:
Allison Berryman wrote:
If you participated in our Game Testing Program before November 25th, we recommend that you uninstall the game testing client [...] and then download and install the launch game client. Please note: a link to download the launch game client will be emailed to you soon, and we’ll update this post with more instructions when they’re available. The size of the launch game client is approximately 27 GB.
If you have played in our game testing program at any point from November 25th onwards, you will not need to re-install the game client, as you should already have the launch version installed.
See the link for more information, including how to determine if you have the launch version if you're not sure which version you have.