According to author, imprinting happens only in very first time when werewolf sees the girl. So no, Jacob will never imprint on Bella.
According to author, vampires can love never but once. So Bella always will be The One for Edward.
In my perspective I think Edward would wait in the shadows, if Bella ever left Jacob he would be waiting. Edward explains this in Eclipse while talking to Jacob.
the whole story would be messed up nd no nessie
i think that the sort would change a ton cuz then there woulden't be as much action and stuff and also there would be no Renesme and if Bella became imprinted on BEFORE she got to Biology class on that first day then Edward would go on hating her and then the story would be just Jacob and Bella but if she did't get imprinted before she got to class then the same thing would've happened on that first day everything would go the same except that when Bella went to La Push and got imprinted on then everything would change and Edward would just be her friend like Jacob is Bella's best friend. Maybe Jacob and Bella would get a kid and Edward would hook up with her. If it was a girl
Well... if Bella decided to continue being with Edward i guess Jacob would surely suicide, cause he wouldn't put up with it... If Bella decided to leave Edward (i don't think so), they would be a great couple...
Jacob and suicide?? Never. (He would not do that for to please Edward.)
I think that that we would have a totaly new begining,plot,ending, and even a new book in that idea. Edward would proabaly have jacob and bella's kid would be edwards true love instead of it the other way around. But if it were to happen i would cry
The story would turn in Jacob's favor and Edward would go crazy of course.
But I would be repulsed by that. I don't think Jacob is a good match for Bella.
If Bella would imprinted by Jacob...
I do not see any basical changes (except Renesmee part). Bella would still be in love with Edward, and Jacob would become her friend - true friend, not pushy I-want-be-your boyfriend.