In short - Yes it works!
I have installed Visualize it and rendered a few models and I have "only" SW2015. I only played a little so I can not say that everything works but I believe it would.
I'm using 2014 and it works.
You import your models into Visualize which is a standalone program. It can import all sorts of file formats and is not SW-exclusive, and definitely not exclusive to SW 2016. I might be wrong but I don't think it matters much what SW version you are using. 2015 will work, no doubt.
Both Thomas & Andreas are correct here. I did some further digging, and it seems Visualize can import files dating back to SW 2009. So there should be no issue opening up SW files from the last few years into Visualize.
Also, if you have SW Pro/Prem and are on active Subs, you get the Visualize Standard product for free. Simply sign into the SW Customer Portal and click "Download Visualize" and use your SW CAD serial number to license Visualize.
We are also working onm a smoother connection between SW files and importing into Visualize for our upcoming 2017 release (available in Oct!).