If you want to give Battlefield 4 a go to help you decide whether you want to purchase the game or not, a new playable BETA for Battlefield has been release this month for both Xbox LIVE and PlayStation Network and it's available to download and play by anybody that has an Xbox LIVE Gold account or a PSN account.
The BETA only includes the Siege of Shanghai map, and two game modes- Conquest and Domination.
This can get boring pretty quickly, but it certainly gives you a feel for what Battlefield 4 is going to play like. It's important to note that this is an open BETA so that DICE can test server stability, so you may come across bugs and server issues, but you can't really complain for free access to the multiplayer game.
The Battlefield 4 BETA will only be available till October 15th, and after that point you will have to wait for the release date on October 29th to be able to play the full game.
Whilst it has officially been named a BETA, I doubt the gameplay experience will change at launch, although hopefully it should give DICE and EA enough information to dedicate the right amount of servers to Battlefield 4 so that the game's multiplayer is smooth at launch.