Sling Blue will have only 32 matches... That is what Sling customer service told me. As per them, FS1 is only going to broadcast World cup matches live and it is going to broadcast 32 matches live. Rest 32 matches, you have to tune to your local fox sports channel which you can get via antenna. And it is free of cost.

There is another package in Sling tv which broadcasts all 64 matches live (Commentary NOT in English though), and it costs you just $9.99 plus applicable tax. It is Sling World Sports package.

Note: The information is based on my telephonic conversation with Sling TV customer service.