As the YafaRay rendering engine has been added to the source code of the program and it will surely be integrated into the next version of Sweet Home 3D for photo or video rendering with a selector to choose between SunFlow and it, there will be no other public versions of this plugin to avoid confusion in the minds of users.
However, when I have more availability, a plug-in allowing to manage the properties of the 2 rendering engines would be possible.