The charts only show current gen because there is already a lot of cards on it. Another reason is the new cards are tested on a different rig and cpu might affect benchmarks. The 5970 is better than the 6970, certainly not showing its age. Saying that a 6970 is beat by 6870x2 so that's kind of a moot point.
You can google benchmarks or your card vs other's. This site also has a more user friendly interface although I don't trust their benchmarks as much as Tom's. http://www.anandtech.com/bench/GPU11/188