Yes, your bootloader is unlocked, but upgrading from an 4.0.4 rom to a 4.x.x rom will entail doing a factory data reset. Actually, I always do a factory data reset whenever I flash a new rom, even if they are both the same android version, or even when upgrading from an earlier version of the same rom.
Another thing to consider also when upgrading from 4.0.4 to 4.x.x is that since you are coming from Ice Cream Sandwich to Jelly Bean, you will want to flash the Jelly Bean bootloader as well during the process. Failure to do so has given folks problems. So, the short list would go like this, while in recovery:
Code:
Create a Nandroid backup
flash Jelly Bean bootloader
wipe data/cache
format /system just for good measure
flash rom
flash gapps (unless they're included in the rom, very, very rare)
reboot phone
profit
good luck