Official comment

I'm sorry, but the cost and time for the resources needed to develop and maintain a Linux version is not being considered as the number of users does not offer a worthwhile return on investment. I know the response would be "Then make it open-source, let the users maintain it!" but there is significant amount of proprietary code that would never be provided as open-source, so the answer there is also no.
I, on behalf of the rekordbox and Pioneer DJ team, thank you all for your interest and passion in having rekordbox on your OS of choice, but from the corporate side, it's not financially responsible to support it.