Actually, Scheme is more accessible than ever before. If installing MIT Scheme and Edwin/Emacs is too difficult, now there's Racket-SICP, which allows you to program with DrRacket, a beginner-friendly graphical IDE, and actually comes with implementations of some parts of SICP that MIT Scheme omitted, like the picture language and (afaik) some concurrency primitives.

Is Scheme really decreasing in usage? Sure, in recent years there have been high-profile moves to Python at MIT and UCB, but I don't know of any hard stats on worldwide Scheme usage. Not that it matters.