Change: https://gerrit.wikimedia.org/r/336454 (just merged)
Where: All wikis (all.dblist)
When: Any time (the filetype isn't currently enabled on wikis but we might as well be ready when it is)
Backwards compatibility: As far as I know, the only problem might be that files with the 3D type will not have any support - but again, we don't allow these files yet so it should be fine for now. If you're worried about it, wait for the above patch to get deployed.
Testing: Currently underway on Beta.
New columns/tables: No.