It's going to be awhile before there is an official announcement regarding an actual release date for the upcoming Battlefield 4 game. However, during EA's last earnings call, they revealed that Battlefield 4 would see a release sometime during EA's 2014 fiscal year, which runs from April 2013 through March 2014.
With a bit of deduction, we can trim down that range which spans a year. We already know that the Battlefield 4 beta will be kicking off in the fall of 2013. This means that Battlefield shouldn't be released before September 21, 2013. Looking at past experiences, we can use the fact that Battlefield 3's public beta kicked off September 29, 2011 to extrapolate that Battlefield 4's beta will likely start around the same time in 2013.
The beta for Battlefield 3 ended on October 10, 2011 and the game released shortly after on October 25. There's no promise of this being the schedule for Battlefield 4, but it will likely be similar. The one thing that EA needs to do is take their time and produce a better game. There are far to many rushed FPS games on the market.