Unfortunately there are currently only two devs working on this @ryanbg
(he is mostly working on N3) and @Surge1223
(he is mostly working on S4).
Here are the things needed for any phone to be unlocked.
1. Large userbase.
2. Most (if not all) variants of the phone has locked bootloader.
3. No developer edition phone.
4. Ungreedy dev who is not going to sell off the exploit to the oem or carrier in exchange of money.
5. Nice enough "guaranteed" bounty for it to be worth dev's time.
6. Dev who is not scared to be sued by the carrier/oem for releasing unlocked bootloader/exploit/signing key.
And in this case we are missing most of the above requirements, if not all.