The preloaded blockchain would be a blessing. Here 5 hours of blockchain download and still more than 70 weeks missing
about super disks: maybe in the future decades paralelization and cloud computing will be the new paradigm, so it is possible that the 185tb will be a luxury item used only for servers. I think that is more promissing work in the bitcoin protocol, to develop something more scalable with time and more paralel-friendly, to rely on hardware development. In last decades algorithm development has been more responsable for gains in performance than hardware developments
the idea of nodes is to ensure history cannot be re-written. imagining a fture where the blockchain is accessed via a cloud service is not good.
basically your talking about everyone relying on blockchain.info as the ledger. where only blockchain.info has the ledger and we just use apps to read that ledger.
if blockchain.info was the only source, they could change a unspent block from like 6 months ago, altering all of the chained inputs before it and because no one else has a copy to compare it, we would all believe it to be true. and because miners were making new blocks based on a blockchain that is only stored by blockchain.info, they would accept the new blocks as the chain is complete.
this is why not only do miners needs to stay decentralized below 51% control of hashing to minimize a notorious attempt to alter new blocks. but the ledger needs to be decentralized via multiple nodes to ensure tweaking of bitcoin historic blocks does not occur either. thus nodes do still need to exist.
(which originally sparked off the debate about block storage in the future, which in this topic was quashed due to large storage availability)
Not sure even I could get that much porn onto a drive that big. 
