You can add this to the growing line of professional apps that Apple has killed off without warning for users - Shake, Final Cut Server, Final Cut Pro 7, DVD Studio Pro, etc. It's one of the reasons that I am not a skeptical Apple software users. Any Apple software I use I do so with the intent of not marrying myself to it because inevitably Apple will pull the rug out from under you.
At least this time it appears that Apple will give users a way to migrate their libraries from Aperture to the new Photos app. Something I wish would've been allowed when FCP X was released in 2011.
This is also a great time to add, if you're not a Lightroom CC user there's no better time to join up!