We only provide instant confirmations for bitcoins we know that are going to get included in a block long before the nlocktime will expire allowing you to spend them.
How long before, because that would make it impossible for people to spend their coins at all during that period, which could be annoying.
Also, does this mean that to verify a transaction can be considered instant, the merchant has to check with your servers and there is no way of verifying this independently? Isn't this a serious privacy problem?
probably that is the right step toward solving the transaction speed,albeit by a slightly more centralized workaround,it reminds me of a comment I made almost a year from now:
