Theory Vivi will be kidnapped by the world government

[meho_meho]

Luffy said he wants 10 crew mates, so that means there's a place for only one other member.
based on the fact that all current members knows Luffy's dream, & that the last member should be strong, so that it balances the scales with BBP who had Kuzan as a new member, we can clearly see that the 11th straw hat will be Yamato. this means that Vivi will not join, so where will she go? the only conclusion that comes to mind, is that she will be kidnapped by the government.

 

[Yoho]

Luffy wanting 10 crew members should be taken with a grain of salt

Yes he said that but that was nearly 30 years ago Oda may have changed his mind about that in that time

And technically he already has 5600 crew members

Although not apart of the core crew the grandfleet is still part of the overall crew power of the strawhats