I hadn't heard an announcement about this yet but all I can say is thanks to HBO for bringing back this excellent show. While the first season was a hit, it was VERY expensive, which almost caused HBO not to bring it back. I guess those DVD box sets sold well enough to get us another season.
And speaking of that boxed set, I bought it, it's excellent. I suggest buying or renting a copy, it's some of the best drama on TV (though definitely not for kids).