Luffy said he wanted at least 10 crew members. So it could be 10 or more.
Actually the "at least" part only comes from a specific translation. Other translations, like the one from Viz, have said that Luffy thinks that "about" ten members would be fine.
I think most people believe that it'll be Luffy and his 10 strawhats vs. BB and his 10 titanic captains. But we're not guaranteed 1 v 1 fights for everyone and the total count for "BB and his 10 commanders" could easily change.
But considering how much this series likes having 1v1 fights in arcs like Arlong Park, Alabasta, Enies Lobby, Fishman Island, and Dressrosa, it is very probable that we might see everybody get 1v1 fights. None of those arcs had EVERYBODY fight since there would always be one or two stragglers being captured or only fighting fodder. Yet we should remember that this is still an action-adventure shonen at the end of the day. It would make sense for Oda to go out on giving all of his beloved main characters a fight.
And I don't think it's likely to change at all. Shonen antagonist groups that specify numbers like that in their titles never change the total number amount of their roster. They can decrease as they are defeated one by one, but they will never increase. You don't hype up how there are ten intimidating people only to bump that up to eleven or twelve for no reason, it's just weird.
And Blackbeard appears so rarely that it's unlikely for him to want to recruit somebody new out of the blue after the timeskip. Especially when we still don't even know the new member who joined over the timeskip to make the crew have eleven members instead of ten.
Is Aokiji one of the captains or is his just an ally? Will Aokiji fight alongside them or eventually betray them? Is Strong included in BB's crew strength?
Definitely an ally. And he will definitely betray them. Oda isn't going to have Kuzan change from not liking Sakazuki's harsh methods of brutality to not minding Blackbeard until the end of the story lol. And Stronger is never listed as a character in any of the volume bios/table of contents when they include the Blackbeard Pirates. He didn't get his own title card either while Doc Q did. Stronger is only an accessory to Doc Q.
I'm now more inclined to believe that it'll be Luffy (#1) + 11 nakama + the Sunny (#13) as the numbering of the Soldier Dock system makes no sense post-TS. The default is 1 and 3 which is pretty consistent. It only made sense pre-TS with the dual "0" channel docks (012034…). I don't even know what the ordering is now, I think it's 125346. Obviously "56" is symbolic as it reads "gomu". The "13" will probably end up being symbolic for the ship being the 13th member -- the most forgotten nakama -- and the total crew count (including the ship).
Why does the Soldier Dock System have to matter at all when predicting how many crewmates there will be?
We also never got the Strawhats zodiac animal signs in the SBS which I imagine someone would have asked at some point when we already have horoscope-type stuff like their blood type personality traits. Obviously Luffy is Monkey and Zoro is Tiger. If Oda included it in the SBS it'd be a major spoiler for crew count (12, not including the ship).
That is also rather random.
In all seriousness can't she just take a vacation..
Think about it like this. Wouldn't it be kind of lackluster if the Straw Hats are on their way to Raftel and declare their dreams around a barrel like the end of Loguetown only for Vivi to go "I want to protect and govern my kingdom, meaning that this crew is only a means to an end for me eventually leaving as I am obligated to my people more than myself or any of you." It stands out too much against how selfish each Straw Hat's reason for being on the ship is. And I also feel like it would sort of spit in the face of how significant the reason for Vivi staying behind in the first place was in wanting to be a princess for her kingdom. Having her still technically join near the end of the series feels like a token gesture without much meaning behind it besides fanservice.
It might defeat the whole purpose of the thread but I just don't see a newly introduced characters joining with presumably only two arcs left before we reach the end. Neither does it look like Oda will give such a dedication as a flashback with whole arc revolving around him/her to a new character, which has been the case for the rest of strawhats. He's already got remaining Supernovas and whole shenanigans he's laid down to resolve y'know.
You mean like how Brook joined in the arc right before the Straw Hats got separated for two years? And all of Fishman Island didn't revolve around Jimbei. If anything, Otohime and Fisher Tiger were more of the main focus while Jimbei was more of a witness that wants to preserve the legacy of their ideals. Also take note of how Water 7 and Enies Lobby balanced having flashbacks for both Franky and Robin.