A Sins 2, or at least a rebuilding of the Sins engine for 64bit seems like a no-brainer to me.
Interest in the game is still strong after all these years, and so developing a new one would be pretty low-risk. I think the IP is pretty unique and attracts a wide audience because of it, including the recently invigorated Homeworld community. There are also pretty much no direct competitors for a E4X/RTS game, especially not one in space.
Also the potential for expansion and improvement over the last installment is so obvious: New game modes; better RTS elements; a possible campaign...the list goes on