Do you still think we'll get a last member after Jinbei?
I'm conflicted on that. Luffy's original promise and the number of BB's crew makes me think we're still gonna get 10, plus Oda's original height chart sketches have conveniently missing gaps where someone was erased (Jinbe obviously, but room for one more still) but Oda's intent to speed up to get the end makes that a little tougher to judge. Oda's having trouble juggling the characters he has and Kaidou was always kind of the last obvious stop for a newbie. and if there's really only 5 years left that not so much time and really if we need that extra we can always just put Vivi forward and say she trained during the tiemskip..
But if its actually 8-10 then there's still plenty of room. Pick up a unconventional viking from Elbaf, pick someone up from random island we don't know about yet (there's gotta be at least one more surprise locale) , Davy Back someone out of Shank's crew, someone they find at Raftel, something. There's still time and space to get one ore but it needs to be soonish because it IS getting to the endgame now and getting the last member during the world war doesn't work..
I can easily see a situation where when Franky joined, we had (at the time) gone a full half the series without a new member, and then just a week later Brook showed up.