Sony's got a new 4.0 update coming to the PlayStation 4 and you can sign up to beta test it. What does the update have? We don't know as there aren't any details. But, if you feel adventurous and would like to try out what they have, just head on over and sign up.
There's no risk in testing out the 4.0 update as you can roll back to 3.55 anytime. If you don't like it, just revert back and you're good to go. Signups will close once the beta starts, so I wouldn't wait if you were thinking of trying to get in.