Camera Raw version 7.x only works with CS6.
You need Camera Raw 7.3 (CS6) or DNG Converter 7.3 or Lightroom 4.3 to open your 6D raw files, because it did not exist before these versions. Camera Raw updates are not usually provided for old versions of Adobe software.
Propriety raw format support can only be added after a new camera's release, unless manufacturers broadly adopt the DNG format as an alternative. Fortunately, DNG Converter is free, and you can use this to create DNG files from your Canon's raw files, to be opened in any version of CS/Lr.