This year they will have 4 pins as in the past, each will be at a different park. If you want all 4 then you will have to park hop to each park to get them. The edition size is 3500 of each so they should last most of the day, but don't forget, there will be tons of us "crazy pin people" still there from the Star Spangled Event on the 29th. That means we all will be running around from park to park trying to get those pins ourselves.
The pin for epcot will have Figment on it and I think that will be the most popular. After that of course MGM will be Mickey.(my personal favorite, but I guess I have to bend to the masses when it comes to pin buying.) Tinkerbell will be at MK, and Simba at AK.
I am sure they will also have some kind of t-shirt either with the 4th of July or some kind of American flag decoration if you are not a pin person, or you can pick something up at your local TDS.
See you there. Peggie