With the developing of off-chain solutions such as the lightning network, I don't find this a proper way of maintaining the security. Despite the fact that blocks' size has to touch the limit which will double every four years, there will be more off-chain transactions than the on-chain ones. It's not practical to have a dozens of terabytes weighted blockchain, because then we'll have to face other issues. (decentralization)
There isn't any problems with a
sustainable block size increase. It is ridiculous to be relying solely on off-chain transactions for the average person. Just because off-chain transactions are better for smaller transactions, it doesn't mean that there isn't any need for on-chain transactions. The problem with bigger blocks is almost always over-blown. There is no such thing as decentralization when it is far better for an average Bitcoin user to be running an SPV client instead of a full node. Storage size is obviously getting far better, either in terms of storage density or costs so that isn't really the issue here.