In the article they mentioned that they just assumed that a 4k 2 hour long movie is 14GB.

That's more what I would expect out of a 1080p movie on a disc. If I have 200TB to play with, I'm not going to care much about compressing the video any more than what the disc it originally came off of was at since artifacts could be introduced. Sure, I probably wouldn't notice most artifacts, but with that much storage even the massive 100GB rips would be a drop in the bucket so why risk it?

Could we see these as competitors to HDDs? 200TB is friggin insane, at a good price you’d be spending 2 grand on that much HDD storage.

I doubt it would compete with HDD for home use. Loading times off of optical discs are atrocious. Just archiving data, sure, but my HDDs actually still have games on them that I run. Old games, sure, but not something where more storage would be worth the reduced read/write speeds. Maybe for a home video server, but that's about it, and there's going to be some significant loading compared to current servers with HDDs.