Storage isn't the real concern. It's RAM (in the short term) and bandwidth (in the slightly longer run).
RAM is cheap and getting cheaper. Bandwidth is cheap and getting cheaper.
At larger blocks (hence more tps) and larger databases, SSDs will be the only way to go. You can trade SSD for RAM all you want, but the truth is that expensive resources will be needed that are not easily available. Hence, decentralization goes down the drain.
For Bitcoin to be bitcoin, we need average JOE to be able to run a full client easily.
The expectation that the future health of the network depends upon people who will not spend 0.2 BTC on their machines is ludicrous.
No doubt those are becoming cheap and limits will have to be raised at some point. But this is not it.
At 1-2 $ per transaction, confirmation time is 10-20 minutes.
The rest are people who won't pay either because they are not in such a hurry, or because they are just spammers. No need to fill up our disks with that.
look if a spammer is willing to pay 50cents pre TX and help support the network.
i'm OK with that.
but we all know this isn't spam...