Read through that entire thread with respect to AFP. Seems like a low number of people are requesting the upgrade (in fact, you were the only one asking for an upgrade, it appears everyone else was just asking for us to not drop support for it entirely). I think we'll need to see more folks rally behind the cause to bump this up in the priority list of "to dos". I realize Tom may have made a commitment here, but we're looking out for the best interests of our users as a whole. Many users are reporting that Time Machine works fine under the current unRAID implementation.
Again, not looking to drop AFP here, just trying to understand why we need a clearly dying protocol to be upgraded right now.
EDIT:
As for Samba/NFS, I don't think you can make a case to say we should update AFP (a dying and terrible protocol) because we've updated other protocols so much. Samba/NFS = more popular, more widely used, and is definitely going to be supported longer. Apples (no pun intended) and oranges.
I would definitely like AFP to be updated. AFP is the only protocol that works correctly with iTunes, as well as TimeMachine. Apple's SMB implementation is good, but has problems.