I have found a way to convert the "Abbey Road Drums" series into the new "Abbey Road Drummer" series, without having to download dozens of GB again, and wanted to share it.
Important: This is NOT a scene release, nor an official update from Native Instruments!
It is a workaround based on my personal experience.
1.) Remove the old library from Kontakt, by clicking on the small symbol on the right bottom of the library wallpaper, and choose "Remove library".
Delete the old nkc and nkx info-files in the library folder. Namely: "Abbey Road Modern Drums_info.nkc" and "Abbey Road Modern Drums_info.nkx".
2.) Put the folder "MIDI files" into the "Abbey Road Modern Drums Library" folder, next to all other folders; replace the folder "Instruments" with the one you find in the download.
3.) Place the file "Abbey Road Modern Drummer.nicnt" into the same location (inside library folder, next to all other folders).
4.) Put the file "ARD_Modern.nkr" into the "Samples" folder.
5.) Import the library with "add library" into Kontakt (you need the latest Kontakt 5!). You should see the updated wallpaper already.
6.) If you load a patch, Kontakt won't find the samples, so you have to do a "batch re-save" first.
Select a patch, then click on "Files -> Batch re-save". The "missing samples" window will appear. Click on "browse for folder", and select the folder of the library, to show Kontakt where the samples are. It will scan the samples, and then do a batch re-save (this can take a while!).
7.) Voila, enjoy!
You should be able to load the patches now, and use all the new features, like the grooves and effects.
It worked perfectly for me, but of course I can't guarantee that it will work the same way for everybody.
Many thanks to member valwello for providing the files