I have a few of them, so I'll just list them. WARNING MIGHT BE SPOILERS!!!
1. Marriage Lola's mom is one of the three remaining Yonkou (now that Whitebeard's dead)
2. To gain Yonkou status, he has to have islands under his protection. He'll name Skypiea, Drum, Arabasta, Commi, Fishman, and Elbaf, among others.
3. The tenth Straw Hat will be Perona. Reasons: A third girl on the team, we know Perona's dream and just being around Sanji would get her close to it (since he's devoted idiotically to any attractive female and Perona's super adorable), Perona wasn't originally a Peace Main but only joined Gecko Moria because she thought it would be fun. Joining Luffy would be more fun, and she'd get a servant like she wants (as I said, Sanji).
4. Boa Hancock will not join. She kicks seals, puppies, kitties, and does other evil things. She is not a Peace Main, and all other Straw Hats and their allies are. After Luffy's recovery, she will stay on Amazon Lily.
5. Usopp will learn various new tinkering ideas from Heracles on the island he got sent to (forgot its name). One of these new things he learns to make is armor that will not break during combat, much to Luffy's enjoyment (since Luffy loves armor but it always gets destroyed).
6. Besides idea 5, each Straw Hat gets more powerful at the island the were sent to by Kuma, who was acting under orders from Monkey D. Dragon to appear to join the Marines so when the time came, Dragon's son and crew would not be defeated when it seemed inevitable, but instead grow twice as strong.
7. Luffy will get 12 crewmembers including himself. I say 12 because I think Perona is obvious (10), but he doesn't have a giant (11) or fishman (12) yet.
8. Luffy will eventually get an army in addition to his 12 member crew (including himself and not including the ship). This will include the santoryu (thousand year dragons), giants, skypeians, and many other nations he already helped.
9. ONE PIECE is not physical treasure. In episode 400, what Silvers Rayleigh said, in addition to the exact words Gol D. Roger said, I came up with this:
The Roger Pirates disbanded on the Grand Line at Raftel. Roger's dream was broken when he realized his disease would not allow him to live much longer. That location, Raftel, is when he realized it. "I left everything I own in One Piece". "One Piece" is the fulfilled dreams of a captain and his crew.
10. The Will of D.
Gol D. Roger's dream was to sail around the world. That dream was taken up by Luffy. Monkey D. Dragon's dream, of what I guess at, is to collapse the World Government. Saul D. Gaol was the giant that inspired Nico Robin to search the seas for nakama, and live. Marshall D. Teach's dream, I assume, is to create and lead the New Era. Monkey D. Luffy has absorbed some of these wills, and I assume will take up the others as well, as the original holders of those wills die... I'm not entirely sure on Portgas D. Ace (aka Gol D. Ace)
11. Usopp and Franky will make Zoro a new sword which will be so amazing, it's a Named Blade. It will be made of Sea Stone.