Hello,
I have just commited portal 2.4 binaries.
To run it, best delete the current installation and do a new maven install && maven all.
Many things aren't working yet, the full list of builds that are turned off is localized in the "TODO" file. So if you want to work on portlets or sth like that, don't update yet.
Also, clean your database or migrate it using the migration webapp (the migration must happen before running portal 2.4 for the first time - I haven't tried it tho ;) )
--
Adam