Beta test participants are not under an NDA, so we should start seeing more content like screenshots and videos soon. Live streams of matches will also be a possibility.
It won't be long before other Starcraft 2 players are invited to join the beta, but you'll need to make sure you're opted in to receive an invite. You can do this on Battle.net.
Starcraft 2: Heart of the Swarm hasn't been given a release date yet, but we should expect to see it complete by the end of the year or at least early Q1 2013.