needs updated
Nice checklist, but it needs updated - even with POP/IMAP enabled for the domain, there's no longer a tab with "Forwarding" options
The only workaround I can come up with is changing the password for PersonLeaving and having Successor (or supervisor) access the mailbox directly - this would be for a limited time, since you don't want to tie up a user license indefinitely.
And in my firm, the supervisor generally wants a copy of the entire mailbox (of PersonLeaving), so we're going to have to come up with a way to generate that - when we were running Exchange, we just connected Outlook to the mailbox and exported everything to a PST file. Now it looks like we'll need to use the Google Apps Sync for Outlook to do the same thing.