I think it's more that a 300GB game will have 300GB of unique assets, instead of taking up the same amount of space and having half that.
If anything, this will be a boon for the PC hardware market. Now all the PC ballers are going to need to upgrade to a new high speed storage solution. Although, I guess this isn't a unique situation. Games loaded way faster on the Sega Genesis than they ever did on a 486 PC, after all.
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