First of all, there are many people that the Straw Hats are going to fight, people that are going to be seen in a flashback, and people they are going to meet. Some of these people are:
1. Blackbeard Pirates: fight
2. Lola's Mom: Meet
3. Shiki: Fight
4. Dr. Vegapunk: Meet, and/or fight.
5. Fisher Tiger: Flashback
6. Coby and Helmeppo: meet, then fight, then meet again.
7. Akainu: Fight!!!!
8. Aokiji: Fight?
9. Kizaru: Fight
10. Luffy's Mother+Grandmother: Meet
11. Other 2 Yonkou: Meet, and possibly fight?
12. Shanks: Meet!!!!
13. Monkey D. Dragon: Meet
14. Laboon and Crocus: Meet
These are the ones I can think of, if there are any I missed, please post them, and tell what the Straw Hats will do when they meet up! See ya!