If it's out for delivery, you'll be getting it today.
They have different trucks with specific routes and different priorities so it's possible the truck you saw was delivering something with a very pressing time issue like express, next day air, same day air, etc. with a deadline before the usual 8pm.
During the holidays, some delivery trucks work until late so they still have several hours to deliver your parcel.
We have had a few USPS trucks come by our house in the early morning and not deliver our mail, they're most likely either picking up packages that were scheduled early or delivery early morning express, which has a time guarantee.
Hooray for ahead of schedule deliveries!!
I should note that if it was shipped with FedEx Smartpost, USPS is the one who does the final delivery of the parcel.
Post Merge: December 08, 2014, 01:08:50 PMSorry for all the edits, my brain is a big mess of ㄴㅅ엉hevdhdshsgsfs모튜너혿ㅎㄷ right now.