Titanfall community manager indicates a beta is possible
Respawn has already said that they're not planning to do a beta but Abbie Heppe, their community manager hasn't ruled anything out completely.
They are currently running a top secret alpha technical test on Titanfall spawning numerous leaked videos on Youtube and other video sites which Respawn frantically chased around to get removed.
People still want a beta though and a fan asked Heppe on Twitter which prompted the coy response, “it's possible”.
Doing a beta certainly wouldn't do them any harm especially with the furore surrounding their choice of a six vs six player cap in games and their producer Drew McCoy talking about how difficult it is to market the game because of its lack of single player.
There's still time in between now and the game's release date in mid-March for Respawn to squeeze in some kind of beta. Remember, the Battlefield 4 beta ran until the end of the game's launch weekend.