Thanks for your explanations. However, as mentioned in my last message, the problem is now that the installer doesn't install anything. When I launched the installer for the latest versions of ViewPoint and FilmPack, there was no copy of PS CC 2014 installed on my system, only PS CC 2015. The previous versions of the ViewPoint and FilmPack plugins were correctly installed in the PS CC 2015 plugin folder.
So the installer should have detected the PS CC 2015 folder and should have copied the ViewPoint and FilmPack plugins to that folder. But it did nothing and the previous versions of the plugins were not updated.
I repeat : if the installer is unable, for some unknown reason, to detect the PS CC version and plugin folder, it should at least emit a warning so that user knows that the plugins were not correctly updated and that he should install these plugins either manually or via the method that you described.
The DxO installers always had a problem detecting which version of PS is installed and determining into which folder the plugins should be copied. This is not new but I think it's now time to fix this. Other software don't have any problem doing this.