I'm thinking about services like Amazon S3 and Glacier here, together with whatever competition appears. I presume that at this level, what matters is exabyte level storage hardware (perhaps a robot-managed room of archival discs or tapes). One where the provider can switch technology every few years, and customers never have to notice.
At capacities on the level of terabytes, we're getting to the point where upload bandwidth isn't so much of a bottleneck any more, aren't we?