It probably depends on 1)How far away you live from the USCIS office and 2)What time you have your interview.
If you live more than 4 hours away you'll probably get a same-day oath. If your interview is early in the morning and you pass and there are no issues, you may get a same-day ceremony. I think it's at 1:00.
I have my interview in ATL tomorrow (1/15) and it's at 10:45 in the morning. A same-day oath would be nice, but given that it's late in the morning, I'm not holding my breath for it. And I don't live terribly far away, so the odds are that I'll have to go back.
If I do land a same-day oath, I'll be very pleasantly surprised.
