>I doubt that there is any difference in a D610 NEF.
Unfortunately, every NEF incorporates a camera model ID, which needs to be recognised by the processing software before the file can be read. ACR/Lightroom don't yet recognise the D610, but as Rick says an update should not be far off.
Alternatively, there are reports that modifying the EXIF data with an editor to say "D600" will allow the NEF's to be opened - check this thread a little way down the page.
There may be no difference in the camera or on Nikon's end, but it sure is not the same in Adobe's mind as the D610 raw images won't even thumbnail in the import function much less open in the development mode.
Because Attitude is Everything ......LiveSTRONG....Mike