Don't you think it would make more sense to keep the tried and true story line about their vendetta? You might think that everyone's sick of that as it's been done to death, but realistically it's only a fraction of the fanbase who feels that way. Mainstream audience would eat that up, because it's 80% of what they know about the franchise - those two feuding ninjas.
Why take 2 steps back, though, when that vendetta was settled in MKX?
Makes no sense, imo.
Shinnok is just a severed head and Quan Chi is dead in MKX.
Their source of "revenge" is dead, and there's no reason for it.
Had Quan Chi still lived in MKX and none of the stuff between Sub-Zero and Scorpion happened in the last game, then I could see the point of chasing him down and having the 2 get together to form an uneasy alliance to take him down in a side-story game.
Once again, though, most of the key characters that would make a Scorpion and Sub-Zero game interesting are either dead or out of the picture (Shang Tsung, Sektor, Smoke, Quan Chi, Shinnok, The Lin Kuei Grandmaster) and Cyrax is AWOL.
Shaolin Monks made sense because it took place between MKII and MK3, and that story between Liu Kang and Kung Lao during that era had not been explored.
What is there left to explore between Sub-Zero and Scorpion?
- Scorpion's death at the hands of Bi-Han?
Done.
It was explored in MK1, MK9, MKX and in Mythologies: Sub-Zero.
- Sub-Zero working for Quan Chi?
Done.
Also explored in Mythologies: Sub-Zero
- Scorpion seeking vengeance on Sub-Zero for the false accusation of Sub-Zero killing his family and clan?
Done.
MK1, MKII, MK3, MK4, MK9 and MKX covered all of that.
- Scorpion forgiving Sub-Zero and working together to take down Quan Chi?
Done.
MKX covered that.
These's nothing left to tell from the vendetta between those 2, and for once, that's actually a good thing.
After MKX, I'd rather have any other 2 characters aside from those 2 getting an action-adventure game.