You can sign up for it now, maybe
Electronic Arts is sending invitations to an alpha test of Titanfall on Xbox One. Origin players with Battlefield 4 appear to be the ones being selected here, however, the alpha will be "extremely limited" according to the publisher. For what it's worth, there's a link to the registration page accessible even if you haven't received one of these emails. Couldn't hurt to sign up.
There's been a healthy amount of skepticism concerning Titanfall, which, fair enough. It's probably for the best that we don't get too caught up before playing it or any game for ourselves. That also goes for blindly hating it. The sooner we can all play this damn game, the better.