We have just planned a last minute trip to Disney January 1-5. We’re still trying to decide between 3 days at Disney or 2 at Disney and 1 at Universal, so we haven’t bought our tickets yet and haven’t been able to check FastPass+ availability. Is there any chance of getting any FastPass+'s at this point?
They hold back some FP for day of, so yes, you will be able to get some. Maybe not for the hardest to get attractions, but people change their plans all the time so you never know what will show up.
I don’t do Universal so I won’t try to tell you much there. WDW however gives you better ticket prices for every additional day you pay for. If you go 2 to WDW and 1 to Universal you will pay max prices for each days tickets. Other than that I would refer to what TheKarenD posted.