A future direction which might be interesting would be to expose the ACS 4.0 core's API to the AOLserver PHP, Python and (when available) Perl modules, so one could use the ACS 4.0 APM (package manager) to mount packages written in those languages.
Then authors who want to write modules for the ACS but don't care to learn Tcl could use their favorite language du jour.
Something like this is likely to get far more support within our OpenACS group than attempts to rewrite the entire thing in Perl, PHP, Python etc.
I also have no idea at this point as to whether or not it is a practical option...
