This would actually depend on how you define "deflationary crypto." If you are being purely technical, it wouldn't be absolutely deflationary until the final block is mined. A slightly less severe definition (more accurate?) would be when the estimated amount lost per year exceeds that which is being created which will occur prior to the final block is mined. The loosest definition would be when the mining reward is slashed enough to impact the supply in the market enough to create a supply/demand imbalance.
This would actually depend on how you define "deflationary crypto." If you are being purely technical, it wouldn't be absolutely deflationary until the final block is mined. A slightly less severe definition (more accurate?) would be when the estimated amount lost per year exceeds that which is being created which will occur prior to the final block is mined. The loosest definition would be when the mining reward is slashed enough to impact the supply in the market enough to create a supply/demand imbalance.