The steps to upgrade openacs.org to 5.3.1 are as follows. I just keep this xowiki page for the record, so I remember what has been done and make this maybe a good guide for the future.
This has given you an installation of openacs.org running on the latest packages. Now we go for the other parts that need to be done
We need to make sure that the new site master template is working with the changes introduced by ZEN. Taking into account that the website is running on legacy code, this might be more of a challenge than initially anticipated.
If we want to drop ETP in favour of XoWIKI, we either need a converter or do this manually by hand. On cognovis.de I did this manually for about 60 pages and it turned out not too be too much time, so doing it hand by hand might actually be faster. But still, someone needs to do it :).
As some of us want to use Project Manager to organize other efforts in the community a little bit better (and be it just to have the laundry list in bits and pieces, so people can go there and deal with it), I will install PM on openacs.org so people willing to collaborate this way can do so. Probably with an integration into XoWIKI as well, so we have a wiki per project (or at least a wiki page per project).