...Whether you chose to incorporate a canon bit in your game is, of course, up to you. But if MgT printed it, it's part of the current canon. ...
As I understand the several games, there are matters of canon that don't necessarily transcend the game they're in. GURPS has a whole lotta those, for example, starting with a living, breathing Strephon. I am most familiar with CT and becoming gradually more familiar with MT, but my knowledge of GURPS, Mongoose, TNE, T4, T5, and so on is very limited. If someone says something is canon for Mongoose, I trust that it is canon for Mongoose. Whether that means it automatically exports over into the CT universe as canon - well, knowing very little about the Mongoose end of things, I don't know the extent to which that is feasible or even desirable. Only Mongoose source I have is their High Guard, which is actually rather good but it would be very difficult to make some of that material translate over to CT. I can therefore only say that because it is canon for Mongoose but not mentioned in CT, it is game-dependent. Nothing stops any gamemaster from importing the material, any more than anything stops anyone from playing the GURPS milieu using the Megatrav rules.
If it is indeed the desire of the community to apply all of Mongoose canon to the CT universe, then I face a rather difficult dilemma - I can't afford all of those resources, and acquiring an entirely new rules system just to keep abreast of new developments in my old one is somewhat impractical. At least in the short term: I do have some interest in expanding my collection in that direction, but I'm thinking I want to explore a bit of T5 before I do that since T5 is rather emphatically being thrust into the CT universe as canon.
...But we're not on the CT board. ...
Nope, we're on the Fleet board, wherein I presume we discuss things fleetish, with no particular canon orientation, where the question arose whether the Aslan would field non-Aslan troops, presumably meaning troops of species other than the Aslan species, where Aramis points out that it's more a matter of culture than species to the Aslan - presumably drawing on canon as expressed in CT AM-1 - and where Whulorigan responds by pointing to a clan of Aslan in Mongoose who enslave other species. Which, as I say, makes it game dependent.
...Except that it takes 2000 years for the Aslans to expand to fill 13 transrift subsectors, which indicates that the number of ihatei who make the crossing is very, very small (or that most of them kilkenny themselves once they're across). Evidently the Glorious Empire got a head start and became too powerful for any single ihatei fleet to handle. ...
A careful viewing of the Traveller Map renders that hypothesis unsupportable. There are a total of 13 worlds within the borders of what I presume to be the "Glorious Empire": one pop code-9, two pop-8's, one pop-7, one pop-6, two pop 5's, two pop-4's, one pop-3, two pop-2's, one pop-1. In other words, about half the "Glorious Empire" can best be described as fruit ripe for the picking. Neighboring them are the aforementioned 13 subsectors full of Aslan worlds.
Powerful among the "Glorious Empire" worlds are - I'm sorry, is - Htourlao, a pop-9 TL E world with a class B port, not building interstellar merchantmen but I think we both agree they could probably build whatever warships they needed. The other high-pop worlds are going to have tech level headaches when someone comes trying to take those low-pop worlds away from them: pop-8 Syoakh is TL C, pop-8 Yero'ilra is TL 7, pop-7 Eikhaaw is TL 9, and below that they'd be doing good to hold onto their own world, much less defend a small neighbor.
Neighboring the "Glorious Empire" in Goertel subsector is Hliyh, a pop-A TL E world, very densely populated, very high tech. Wiki says Hliyh was liberated from the "Glorious Empire" in the "last decade" - presumable some time between 1100 and 1110.
Over trailing-ways, in the neighboring Tlaiowheredotheygetthesenames sector, there's Tyohk, a pop-A TL E Aslan world, and Tlaiowaha, a pop-9 TL E Aslan world - these are quite possibly the places the liberators came from.
Over spinward, in the neighboring Nora'a sector, there's Hreahrya, a pop-A TL D Aslan world, and neighboring Oaiah, a pop-8 TL D Aslan world.
Just to rimward in the Silraaine sector is Irlaiw, a pop-A TL D Aslan world.
In short, the "Glorious Empire," the reviled clan of renegades whose fate now depends on one high tech world with billions of sapients - some of whom are slaves - has tens of billions of Aslan within 11 parsecs of its borders who both hate it and have the power to do something about it.
Now, I do not suggest that the Aslan got together and decided to wage a massive crusade on the "Glorious Empire". I DO suggest that attrition is a deadly thing. The "Glorious Empire" is a reviled renegade clan. It lacks the strength to hold onto what it has. There are powerful neighbors from which forces hungry for land and honor can arise - and those neighbors didn't just show up yesterday. A war here, a war there, 469 years of that, it's a small wonder the "Glorious Empire" didn't meet its glorious end 200 years ago.
I have serious doubts whether that TL7 world could actually resist a space-faring Aslan clan. I'd have expected that cluster to go down when Hliyh got liberated, or very soon after. I'm inclined to believe at this point the "Glorious Empire" would consist only of Htourlao, Syoakh, and the cluster of worlds closest to those two - and I'm still rather surprised they've survived this long. The only thing I can make of it is maybe the neighboring clans don't actually see much glory in fighting the "Glorious Empire"; maybe there's such contempt for the empire of slavers that they only draw attention when something special reminds folk that they're there.
But, that's mostly my bored mind wandering aimlessly. You know me.