I am a long time CARVER owner (20+ years) and something that started at CARVER that has been perpetuated by Sunfire is to call those "Hall of Fame products". I think other companies (Polk Audio comes to mind) call them "Vintage", etc.
I have seen the term "alumni" at other places (can't remember where) but, IMHO, I believe it hasn't caught on because the marketing folks might wonder if they are making the company's current line of products seem like they have not graduated yet or, worse yet, give their new products the status of "freshmen".

Young people who look at some of my old gear call it "old school" - I take that as a compliment.

I am OK with any positive label. I just don't like "retired", "discontinued", "not supported", etc.
"Alumni" sounds good to me. As long as we agree that my 990 is working on its post-graduate.
Heeeey... I just thought of something... what if when a product joins the rank of the alumni it gets a "degree" based on popularity, customers' comments, etc.?

And another one! (feeling creative this morning). Since "alumni" doesn't really sound like an "Outlaw", how about "fugitives of justice"? Ha!
I think we would have to deal with marketing again... Alumni is cool.