Base16, Base32, and Base64 Data Encodings is going to Last Call as a Proposed Standard.
Oh no.
I'm not a 64 bigot, and it's not that Base16 and Base32 are bad, it's just that they're new and I'm afraid of the inevitable, which is, I'll predict right now, that shortly after this becomes a Proposed Standard someone will complain that Atom is horribly broken because it only accepts Base64. Mark my words.