The Blender plugin has been released with the SDK as per version 1.3.1, wich has some big flaws (one of them is the connection of the comp map to the main shader)
Some of those looks like to be fixed in 1.3.2 branch (last commits are more that 2 months old)
Can we still expect support for the plug-in on the GitHub or being released as part of the SDK we have to open bugs here?
Yes disappointed too in the lack of progress on the Blender exporter. I have made numerous suggestions to fix some of the issues. 1.3.2 has a bug in the detail texturing. I believe the connections from the textures to the mix nodes are not correct for the detail textures to show properly.
Now that the Blender exporter is officially part of the SDK, support can be done here.
You can report bugs in the Bug Reports - Art category and use the blender tag.
The final SU13 SDK will come with a 1.3.2 version of the Blender plugin, including some fixes that are not available on the GitHub repository yet.