The History Of Ythrians II

In relation to the History of Technic Civilization, there are seven distinct stages:

humans discover the planet Ythri;
Ythrians adopt Terran technology;
Ythrians and humans jointly explore the planet later called Avalon;
both species colonize Avalonian islands;
both species colonize the main Avalonian continent;
both species resist the Terran Empire to keep Avalon in the Domain of Ythri;
an Avalonian Ythrian spies for both Domain and Empire.
-copied from here. 

Let us expand and refine this summary:

spaceship Olga of the first Grand Survey, under Captain Gray, makes first contact with Ythri;

Ythrians study at the University of Nova Roma on Aeneas and adopt Terran technology;

Ythrians with some human employees explore Gray/Avalon;

an Ythrian spaceship transports Nicholas van Rijn and his granddaughter, Coya Conyon, to Mirkheim;

David and Coya Falkayn lead the joint human-Ythrian colonization of the Hesperian Islands on Avalon, members of each species settling on different islands;

both species colonize the Coronan continent, Parliament and Khruath agreeing which territories each species should settle;

Avalon, where many human beings have now joined choths, successfully resists Imperial annexation and remains within the Domain of Ythri;

an Avalonian Ythrian spies for both Domain and Empire because Merseia threatens both;

Dominic Flandry comments that -

sophonts will survive the Empire and will build fascinating new civilizations;
cultures of mixed species, e.g., Avalon, look promising.

So we learn that:

the bi-species civilization still exists on Avalon in the later Imperial period;
an expert expects Avalon to survive and thrive after the Empire -

- and we want to know what happens after that...