In "Darker than Black: Ryuusei no Gemini", what happens to Hei's powers?
If you notice that at the beginning of "Gemini of the Meteor" season BK-201's star vanishes, and he loses his powers. At the end of the season, 


   BK-201's star lighting up in the sky. 


Each "False Star" has a corresponding Contractor, and they resonate when their Contractor's power is being used. As such I think it's safe to conclude the he has his powers back.