According to this post over at Blue's News, the Steam Greenlight program is going away while a new system called Steam Direct with take its place.
A better path for digital distribution. The next step in these improvements is to establish a new direct sign-up system for developers to put their games on Steam. This new path, which we’re calling “Steam Direct,” is targeted for Spring 2017 and will replace Steam Greenlight. We will ask new developers to complete a set of digital paperwork, personal or company verification, and tax documents similar to the process of applying for a bank account. Once set up, developers will pay a recoupable application fee for each new title they wish to distribute, which is intended to decrease the noise in the submission pipeline.