SpaceX had introduced its Dragon V2 spacecraft, which already can be manned.
The original Dragon design made made the first commercial cargo delivery to the ISS in 2012. Untilnow,Dragon has already made three of 12 NASA contracted missions to the ISS, carrying cargo but not astronauts.
They wouldn't only transport NASA astronauts but those from other countries as well. (The The ISS programme is a joint project among five participating space agencies: NASA, Roskosmos, JAXA, ESA, and CSA.)