It states that this is a fight for the survival of dragonkind yet the Othermind doesn't actually terminate dragons it infects it just leaves them unable to control themselves so the Othermind could and most likely would still allow them to reproduce in order to have more subjects
This is a fight for control not survival
All the threats in the series have been(The only exception is maybe Snowfox) fights for control and not survival(The sisters only wanted to control their kingdom, Darkstalker wanted to rule the continent, the Othermind wants to enslave the dragon race, etc.)
This is part of why I like the idea of a third continent(If it exists) not housing many dragons and instead being dominated by creatures evolved to hunt them as it raises the stakes from a fight for control to a fight for survival
So either the description doesn't fit at all or Tui's gonna shoehorn in some new threat at the end and just invalidate the buildup of taking down the Othermind