Imagine 2 blockchains processing the same amount of transcations. Now Chain 1 is running with ringsignatures and Chain 2 is not.
Now lets say that every year 500 GB of transaction data gets produced and no blockchain pruning and shrinking is available.
After 1/2/3/4/5 years
Chain 1: 750GB/1.5 TB/2.25TB/3TB/3.75TB
Chain 2: 500GB/1TB/1.5TB/2TB/2.5 TB
And this is under the best case scenario that ringsignatures only produce 50% bigger tx. This number can be higher!
-snip-
Will a 110gb blockchain on full nodes really matter by 2019, when everyone is sporting 40tb drives? By direct comparison: Bitcoin's blockchain takes up 0.5% of today's 4tb drives, and comparably Monero would take up 0.275% of 2019's 40tb drives. In other words, disk space and Internet capacity is rapidly outstripping potential blockchain growth.
Ring signatures provide cryptographically untraceable and unlinkable transactions for a small sacrifice in blockchain storage in a world where disk space is not at a premium.
Sorry to spoil it for you, but most people do not have money to afford a 1TB thumb drive nor a 6TB HDD. In my country I rarely see people who have a 1TB HDD or higher (excluding myself). How do you plan to have a wider adoption? Although you never know, we might have 40TB drives we might still be stuck with the current limitations (look at batteries - minor/none improvement for years).
There are other ways to provide untraceable and unlinkable transactions. While ring signatures might bloat the blockchain a bit, they could do for now I guess.
But they will be able to afford them in 2019. I think his point was that if he has these today then by then storage will easily cover the needs of the blockchain for many people.