I tend to agree that silence from canon in Traveller should be interpreted as a statement about canon.
We have infrequent or hazy references to things that aren't fully realized, and yet were obviously in the authors' minds, and are probably canon. This is where some holy wars come from. Drop tanks. Artificial intelligence and starship automation. The effectiveness of fighters. 100,000 ton cargoliners. We suspect there's an official "range" of correctness, some configuration that may work the way they were originally intended... or the way we want them to.
But then we have things which were never mentioned, or not strongly hinted at. Stutterwarp was never called part of the OTU. Canon is silent. Does that mean that stutterwarp is, in fact, present in the Official TU? (No.)
Do we have lightsabers? (No.)
Do we have the "Mos Eisley Cantina effect"?
No.
Are there significantly more than 7 or 8 "native" sophont homeworlds per sector?
Not in the Marches.
Not in the Imperium. (What is that reference about the Vilani running up against a lot of initial competition?)
How about "not anywhere"? I'm less pessimistic, but I know the Imperium isn't very highly polysophontic.
Here's how far I will stretch it: I could see 16 current sophont homeworlds in the Marches -- appx one per subsector -- if it's done well without disrupting what I know about the Marches from the adventures. But any more than that really tends to bother me, and I'd rather see fewer (i.e. 8 or 12). I don't mind mixing in pre-sophont species and extinct sophont homeworlds to that mix, as long as there aren't too many of them.
And I think that would count as a retcon.