said by 88615298:3000 Blu-ray movies( if there are that many )assuming your 31 GB average size is correct is 91 TB.
May titles have multiple discs. I have some titles that have five or six Blu-ray Discs. And the james Bond BD set I'm getting soon has over twenty discs.
Although I have no idea what the actual count is for titles released on BD.
And my 31GB size came from my average disc size for what I have at home. Although I have over 110TB available on my home network, but not all of it is in use.