I considered it in the past, but left when looking at the large amount of files without copyright tags. The problem of mediawiki.org is that they have many files whose copyright status is unknown, but that -unlike wikipedia- were uploaded by there authors (with high probability).
There are old files with unactive authors which would be a pity to lose, screenshots including logos, files with no license by wmf employees...
However, I think it's a good time to begin being strict with the license of newly uploaded images.
Happy New Year!