If you want to hack trying out guile-next, you can't use the geiser package. Fortunately, the git version of geiser supports guile-next / 2.2 / (2.1?) so, here's geiser-next!
Not sure if other people care enough to have a geiser-next package, but since we're Guile based here, I figured other people might want to be hacking trying things out with the latest and greatest. - Chris