Battlefield 4 may have been leaked on Origin, EA's digital distribution service. The link has since been taking down, but earlier there was a message saying if you pre-ordered Medal of Honor: Warfighter, you'd be granted access to the Battlefield 4 beta. That would have been one slick pre-order incentive, but considering EA and Dice haven't even announced Battlefield 4 yet, this seems like some kind of accident.
Electronic Arts president Frank Gibeau did confirm that there will be a Battlefield 4 during a keynote speech at the University of Southern California last November, so we do know that it's in the works. Considering all of the Battlefield 3 premium content that just launched and will continue to come through March 2013, it seems a bit odd that the Battlefield 4 beta would be ready any time soon.
We'll keep you updated on any more Battlefield 4 news as it comes in though, which is hopefully soon.