They opted out from scheme as a whole.

This is reflected by the name change.

http://www.racket-lang.org/new-name.html

I'm familiar with the name change, but they didn't opt out of Scheme at all. Racket still supports both R5RS and R6RS. And before someone starts going on about the "default language" not being Scheme anymore, Racket doesn't have a default language. You have to specify one. Many of the things that have been added to Racket beyond the Scheme standard also have analogs in other Scheme systems.