While this is not an official release date, I'd look for EG 4.2 around the end of this year.
As far as compatibility -- no, EG 4.2 supports only SAS 9.2. You can still have EG 4.1 and EG 4.2 installed on the same machine, if you are straddling SAS deployments. Also, EG 4.1 works with SAS 9.2 on Windows (when both EG 4.1 and SAS 9.2 are installed on the same machine).
EG 4.2 and SAS 9.2 ONLY is good news. That means that 4.2 is going to take advantage of some of the new features of SAS 9.x rather than being limited to the SAS 8.2 feature set; personally, I'd like to see clickable options for ODS graphics....
I was given the impression that EG4.2 would only be a worthwhile upgrade if you were also running SAS 9.2.
I am peeved that EG4.1 seems to like to disconnect the workspace session after 30 minutes of inactivity (when the communication with the metadata layer fails), but I'd like to know if EG4.2 requires SAS9.1.3 and above. If so, I might just stick with EG4.1
It's part of the SAS 9.2 Phase 2 release, which is due to customers around the end of next month (Feb).
We in R&D just signed off on SAS Enterprise Guide 4.2 this week, which means that we consider it ready to go. However, you need SAS 9.2 Phase 2 to take full advantage of it, and it's all still making its way down the pipeline.