You really don't know what you are talking about. The iPhone firmware includes the basedband software. The baseband software is the embedded program on the radio chip. This program is what locks the GSM radio to the SIM card. And THIS is the one the unlock modifies.
All previous firmware updates (1.0.1 and 1.0.2) didn't include updates for the baseband because there was no need to. That is why the unlock till now is restore resistant. It is not because a feature of the unlock but because 1.0.2 doesn't unclude a baseband update.
Now that the unlock was out, Apple had to do something about it because of their agreements with AT&T. So they are releasing a new firmware version (1.1.1) that will include an update to the baseband. Updating the baseband will simply replace the modified unlocked one therefore relocking the phone.
The statement released by Apple yesterday is nothing more than a PR stunt to show AT&T that they are doing something about the unlock. They WILL update the baseband but them bricking intentionally is highly highly improbable.
Then theoretically, we could if the dmg image could be decrypted, take the part of the update that is not updating the baseband, and just update the non-baseband part of the firmware, allowing the new features (if they arn't tied to the baseband update as well, ala PSP hacked firmware.