I think, we had that covered very well in the past. The conclusion - diversity is the key. I have the Cloud archives in the open, NAS with RAID1 - in the house, External HDD's - on the shelves, T-Flash Cards - EDC in my pockets.

The M-Disk looks interesting, especially their subscription (so you don't have to buy BD-writer at all. The only caveat - you will have to pay for the Dropbox account as well, as the content allowance on a free one will barely fill one DVD disk, and then upload your terabytes for many weeks to build a library for M-Disk archiving there... Also, it would be nice to see a third party knowledgeable opinion on M-Disk technology itself, as so far I don't see how it's better from an ordinary BD/DVD disk, especially having the same ordinary BD/DVD writers capable of dealing with these M-Disks.