yah acid is certainly not extinct.
the only drugs ive seen dissapear utterly and entirely are AMT, 5-MeO-DiPT, 2-CT-7, and 2-CB. They used to all be relatively easy to aquire about 5-6 years ago, and since then have vanished from my sight (of course AMT and so-called 'foxy' were easy to get since they were quasi legal).
On the other hand, just in case any DEA pricks are reading this and glowing, LSD, Mushrooms, Heroin/OxyContin, Cocaine, Methamphetamine, Ecstasy, and Marijuana have all become easier and easier to access (LSD being more difficult but not nonexistant) in that time period. In fact, drugs like weed, E, or meth seem to be easier to purchase than toilet paper or chicken breast.
I don't think that ludes has ever been used as slang for speed. Quaaludes are like the polar opposite of speed.
Yah u are right. If people are saying they have 'ludes, they most likely have some kind of benzo cut up and re-pressed into a pill. They were popular back in the 70s, but I think more contemporary downers would provide, shall we say, a greater bang for your buck. I think they are still produced in pharmecutical companies in countries with disadvantaged economic systems, but someone bragging they've done/have ludes is just lame, and pretty much the only reason the term "Quaaludes" still persists in the drug underground.