@Shift:
There have been way too many panels and chapters devoted to his inner reflections to ignore, and this chapter's reminder of Ace asking the crew to look after Luffy, just as he asked of Jimbei, really stands out to me.
I still hold to almost all of the speculation I started a year and a half ago. Little has affected my opinion of what I had presented, just minor details really, and more has come to support it as time went on. Then again, while a lot has stacked up in his favor, that doesn't mean he isn't Vivi 2.0, in that he travels with Luffy for a duration of time and ends his travels somewhere for reason xyz. Like you said, we will be with him for a while, so the speculation will go on, but I still think there is good reason to believe he will join.
@HaxeyeMihawk:
Their seemed to be a clear mentor and misguided pupil vibe going on there and not of two peers or soon to be crewmates.
I can agree with what most of you are saying in that it appears like Jinbei is that mentor-type supporting role, but on the other hand, I think that Oda has gone out of his way to keep Jinbei humble enough to appear around Luffy's level. Even in this chapter we have Jinbei saying, "I won't lose to you in a state like that", as if things could change or would be different under other circumstances. Given Luffy's expected growth is right around the corner, all it takes is an obstacle Jinbei cannot overcome for Luffy to prove he stands above him. Not much different than Franky or Robin in that regard.
@Shift:
Jimbei may be older and more experienced, and his personality is pretty formal, but I don't think such a personality would be unwelcome on the crew at all; if we've seen anything, it's that the Strawhats are made up of all kinds.
This was the next point I was going to make. I would say Jinbei's personality as a whole is what gives people that mentor/supporting role vibe, when that really can all just be attributed to his character archetype; the formality, wisdom, and serious demeanor will always make him appear that way. The important thing, I think, is his view of Luffy; it isn't admiration or favor, it's respect.
"He broke into the impenetrable Impel Down."
"Unbelievable! It takes more than one or two lives to reach this place!"
"My debt to you is great!!"
"Even aside from this incident, I feel a certain level of gratitude… and guilt... towards you."
"I don't lend my hand or protection to anyone but those I care deeply for and respect."
"I have made the decision to protect this boy, even if it means sacrificing my own life!"
"Your confidence to climb over any walls! Your own strength you never doubted!"