My Golden Blood Theory:
So the show has not clarified why Mark is protecting Tong until he is 21. Personally I think 'What happens when I turn 21' should be Tong's immediate next question, but I understand baby girl is going through it with the whole vampires are real, and I'm not actually sick (my whole life has been a lie) and I actually have magic blood that makes vampires cum....thing...
Anyway in my opinion there are 2 ways they could go with this
1. When Tong turns 21 his Golden Blood loses its power, he can live a normal life. This is both less likely and less narratively interesting than my other theory, but not impossible with what little we know of the world building so far
2. When Tong turns 21 his blood will reach its peak power and he will be given to an important vampire who will drain him for his blood's power. With what we currently know: a) the vampire Mark works for is Thara b) Thara's power is weakening it is possible there will be a twist where Thara wants to consume Tong's blood to maintain her strength (and she'll argue maintain peace for vampires/humans) + possible implication of her being behind Tong's parents death for this same reason (assuming Golden Blood is hereditary) Personally I think this would actually be a wicked direction to go in because it means Tong has essentially been raised like lamb for slaughter, protected by Mark his whole life, but only so he can be sacrificed later. which is dark as hell and this is a vampire show, let's get fucking dark.
Mark probably won't know about this if that's the case, but it's possible he's been in on it from the start. Either way, when the reason Tong is being kept alive till he's 21 is revealed it will create excellent angst for Mark and Tong.
It is of course always possible Nakan will remain the main antagonist,as has been implied, be the one responsible for Tongs parents, etc but he could also be a red herring. As is Mark doesn't seem to take orders from him , so it's unlikely he'd be the one to have Mark keep Tong on ice.
(PowerPoint slide ends with dissolve effect)
