As I understand it, without implementing disk-space-reclamation as laid out in Satoshi's paper the system will not scale because the blockchain contains a history of every transaction. Bitcoin has been going a few years at below 1 tps and the blockchain is already over 6GB. At 4000 tps it will be unmanageable.
Again, as I understand it, you can only remove a transaction from the blockchain if both its outputs have been fed into new transactions, and they are buried deep enough in the blockchain.
If I were to split a single bitcoin into 100,000,000 smaller bitcoins and save them for eternity in my "piggy bank" wallets, would that force all miners to save at least that much data for eternity?
In fact, what about the case where a large number of people - without any malice - choose not to spend small amounts of money for a long time. Would this not also break disk space reclamation? Has this been modelled?