Is Linna's death mandatory?! - Where did that come from? If new campaigns try to stay within the lore, their plot should not exclude all possible endings of Dark Messiah!!!
- Can the player ensure that Linna survives? Answer: Yes, they can!!!
- Can the player ensure that Linna dies? Answer: Yes, they can!!!
Therefore, the human faction can fall, or it may not, but it is not specified when exactly (tomorrow or in a hundred years). That is, humans must exist, but it is quite possible that not in the form of a unicorn empire, but as part of something else. Moreover, the fall of the human faction does not imply extinction as a species, but implies a fall as an independent empire.

Level 1 - dwarves (Guards/Legionnaires/Sentinels), levels 2, 3, 4 - humans (Archers/Veteran Archers/Light Archers, Warriors/Crusaders/Clerics, Novices/Faith Protectors/Vestals), level 6 - elves (they will be unicorn riders).