Olin, Roderic, and myself are working on the next major release of scsh. This next version has things like 64-bit support, r6rs support, all done on top of scheme48 1.9. We hope to ship it in the next few months.

If you're interested in participating or testing, head on over to http://code.google.com/p/scsh/

In addition to updating scsh, we're also working on getting MIT Scheme's Edwin editor to run on top of it. Which is over at https://github.com/scheme/edwin48