Some folks (believe it or not) have data caps smaller than that. I believe Comcast has a cap of 250GB. Now, while that seems a lot bigger, it doesn't really take gamers into account.

they sent me a sheet one time saying how I could send 50k emails or download 500 songs or 50 movies with my cap... and game sizes are only going up.

Anyway, a game of that size should definitely be available in a physical format.

How so?.

ConsidEring it will have pre-rendered cutscenes with 1080p quality and a gigantic world with much to do.

Frankly it's already 21GB and only has a handful of ships and locations compared the whole game

Basically, if you stick textures designed to be viewed in 4k, then you are going to take up a lot of space

Also given that such a vast amount of content is going to be included, but not randomly generated, I'm not surprised it's only going to keep growing. They do just need to focus on improving their download speeds, because patches already seem to take all day despite my 120Mb/s internet connection

Meanwhile Elite Dangerous is 4GB, simulating the entire Galaxy.

That's awful, most of the world(even in the West) still has datacaps and slow speed.

And that's huge compared to the original Elite, which fitted entirely on a single floppy disc (less than 1Megabyte!). And that one too simulated entire galaxies.

This is bad news for most people but it's a sign of things to come. BF4 is 65 gigs and counting. By the end of this gen game sizes is going to become an issue.

Because it relies on procedural generation and doesn't have anywhere near the same amount of detail as Star Citizen

Correct on the first part, not so sure about the second
https://www.google.ca/search?q=elite+dangerous+screenshot&biw=1920&bih=1008&tbm=isch&tbo=u&source=univ&sa=X&ei=aowBVZbKBsWbyATWtICwCw&ved=0CBwQsAQ

There aren't that many ships yet in ED as well though. And yes the variation in space stations could be greater, planetary landings / atmospheric flight haven't been implemented yet.  At least I can download it :)