I think the key reason for the $10 bill's current life is Scotiabank. If I recall, many bank corporations rely on secured cash dispensers in order to avoid robberies. They configure the machines to dispense $5/$20/$50/$100 only. $10 bills are the first to be dropped, since most customers do not favor them - at least where I live.
I am not sure if it has to do with Sir John A. MacDonald's likeness - a controversial figure at that - on the older tens, or the fact that the $10 bills have a high percentage of counterfeits that may have tarnished the banknote's reputation, even though a notable woman is now on it. Despite that a notable woman, Desmond, replaced MacDonald, there are still very few $10s being used across the nation. I also realize that the number of $10 bills in circulation had risen over the years but in tiny increments, but do you suppose most of that number is made up of stockpiles of $10 bills that were sitting in bank vaults for many, many years, and the real number of $10 bills being used may be drastically lower than we expect? I can see a likely reason why many banks decided to discontinue ordering $10 bills - most likely permanently.
Scotiabank is one bank corporation that does not rely on such dispensers, though there may be many Scotiabank branches that do not order $10 bills. I think the only thing that will result in a possible demise of the $10 bill will be if every bank corporation relies on secured cash dispensers across the nation, which will only dispense $5/$20/$50/$100 in this day and age. If this happens, $10 bill orders will be dropped by all of the remaining banks, and production of $10 bills will likely cease since bank orders will be zero by that point, and in a matter of time, the $10 bill will likely go the way of the $500 bill and the 50-cent coin.