SOCOM 4 beta dated, PlayStation Plus members get early access
Everyone is invited to the SOCOM 4 beta starting April 5. But you'll have opportunities to get in earlier:
March 15 - Private Beta. "We'll be contacting eligible players soon."
March 22 - PlayStation Plus early access
March 29 - Access included with Killzone 3
April 5 - Free public download on the PlayStation Store
The beta will include all of the game's competitive multiplayer modes -- Suppression, Last Defense, Uplink and Bomb Squad -- playable on two maps: Port Authority and Assault & Battery. It's scheduled to conclude on April 13.
Unfortunately, the beta won't give you a taste of the five-player co-op mode. You'll have to wait until April 19 to try that out.