Few moments ago, Musclenerd has confirmed that the ultrasn0w to unlock iPhone 3GS and iPhone 3G finally got working fully on 4.2.1, so it looks that everything over there going alright, everything on schedule, which means that we will catch new version of ultrasn0w tomorrow (Sunday 28th Nov) as we mentioned before.
Musclenerd: Finally got ultrasn0w working fully on 4.2.1. Apple inadvertently(!) broke ultrasn0w via aggressive compiler optimizationTill know there's no news about iPhone 4 baseband unlock. For now we let you know immediately after the release of the new ultrasn0w, stay tuned.
UPSATE 1: Musclenerd has just confirm via his twitter account that the release will be at 2:30am.
UPDATE 2: Ultrasn0w has been released, Check Here.