Can this be done for my music collection?
I've taken a look here and got a little scared:
How do i convert all my tags to ID3v2.4 (ID3v1 ID3v2.4) - Support - Mp3tag Community
I need my tags to work across MP3Tag (current version), Traktor 3, and iTunes (12.9.3.3).
I'm worried that iTunes will have issues w/ID3v2.4.
This would apply to mp3 files, I think. Flac, wav, mp4 would use their own tag versions.
Set the corresponding option in File>Options>Tgas>Mpeg>Save 2.4.
Select the files and press Crtl-S to save
I wonder why you would want to do that as V2.3 has the best compatibility so far. E.g. WMP in W7 cannot read V2.4 tags at all.
So I would understand if you would want to convert V2.4 to V2.3 ...
Hi ohrenkino - thanks for the quick response. 
Yes - I'm only talking about .mp3 files here. The reason I want to convert to v2.4, is that there are more common tags between Traktor 3, and v2.4. So, tags that I update in Traktor, are updated in the .mp3 file, too.
Compatibility wise, I really only care about compatibility between iTunes, Traktor and the .mp3 file itself.
Many players out there still do not support v2.4. Consider what benefit you are seeking from this before you go ahead.
Like I said above - the only compatibility I care about is MP3Tag, iTunes, Traktor and the ,mp3 file itself. 
You will understand that I cannot give any guarantee that you will achieve your goal in respect to iTunes and Traktor. I can only tell you the technical part of how to convert the tag versions.
If traktor already writes V2.4 tags and iTunes shows them, then there should not be any problem.
If traktor writes v2.3 tags and iTunes shows them, I would not change a thing.