@lkbroach
I see where you're coming from as I guess you get to a point on whether you think the time is worth it to go from a Large to a Gigantic present with the grind. Having some item probabilities listed would be nice as a reference. If my memory serves me correct, Nick went over what was inside the presents prior to them opening last year (unless I'm thinking of the Easter Eggs). He didn't mention specifically what you'd get, but a general idea of what you could get out of it.
Good news though, you're able to build the presents after the 25th! The exchange sets won't be there, but if you are curious on what others are getting from their presents you can always hold off on completing the sets. The presents will automatically open though once completed. Nick mentioned it here: https://www.twitch.tv/videos/846426597?t=00h04m58s