(You could also argue that stack-oriented programming the way Forth
does it has implicit GC...)
I've thought of the stack as a continuation which means Forth programs
are already sort of in CPS, but GC is something different. GC means you
can pass large objects around by reference, copy references freely, and
the GC automatically reclaims objects with no live references. Anton
Ertl (a well known Forth implementer among other things) suggested an
interesting classification of high level vs low level languages.
According to that classification, HLL's are the ones with GC.