Following up previous rumours, EA has confirmed in a press release Battlefield 4 is indeed a thing that's happening, and you can start playing it in beta form as of autumn 2013, assuming you pre-order Medal of Honor: Warfighter Limited Edition. Funnily enough, platforms are again not confirmed, as with the previous Medal of Honor and Battlefield 3 offer.
From what I've been hearing based on alpha footage, Warfighter could actually be a surprise hit, so you may want to seriously consider this offer.
The negative side to all this is it means DICE seems to be abandoning their approach of building the main series games for the long term -- some people still play Battlefield 1942, the first title in the series, for example. While I'm sure for any number of reasons some people will prefer Battlefield 3 to its sequel, pushing it out so soon after its predecessor -- which itself is not even finished -- all but kills any possibility of each game seeing a long and healthy shelf life, and of being polished (at least in a timely manner).