Latest FAQ (link) on NIK software/Google, they mention they are looking into supporting Photos for OS X.
This is better than a straight “no we won't support it”.
If Apple can get the organizational part of Photos as good as, or better than Aperture I think this could be a home run. Specially because all those plug-ins/extensions will work straight into the RAW files and no more exporting TIFF (non-destructive!!).
Let's just hope they don't take too long to get there.