You're posting in all the wrong forums.
M:TG has gone underground, kinda. Well, where I live it has, anyways. I've talked to a lot of guys about the "good ol' days" and there are a lot of people who'll admit to having a Magic deck and a shoebox full of cards. Younger kids don't want to play it, though, and would rather play the gay Pokemon shit rip-off garbage.
They also kept introducing new rules all over the place--alienating a lot of the older players--and started putting rule explanations ON the actual card itself. Then they started introducing crazy powerhouse cards that were powerful all by themselves, not in combo with other things... no more strategy involved. Now they've redesigned the cards completely and they look like shit. It's a pathetic attempt to
There are still a few times I see guys playing at university, but you won't find anyone under 16 who even knows what Magic is anymore. I stopped buying them shortly after Stronghold came out.
You can still sell your cards, but unless they're some of the old pre-4th edition things or the ultra rares, they probably won't be worth very much.