So,we haved Jazz and Ironhide as second in command but who will be next?vote out of Ultra Magnus,Prowl,Grimlock,Scattershot,Silverbolt,Hot Spot
I'm pretty sure Sideswipe became second-in-command of the Autobots after Ironhide's death. After all, he was giving out orders in Chicago from time to time.
Considering none of the characters you propose have appeared in the movies, nor have yet been slated to appear in Transformers 4, this is hardly a productive topic for the Movie forum other than simple fan-hope, which itself could simply go into the Megathread that good ol' TylerMirage has the link for. Besides, as of Ironhide's death in the third film, most fans believe that Sideswipe, or alternatively Ratchet, took over as second-in-command.
Sideswipe is already SIC. Ratchet will never be 2nd-in-command, he's a medic and only a medic he shall be until his death.
Seeing as Bumblebee is usually given a level of autonomy as a scout / due to his relationship with Sam, Ratchet would be the next most senior of Optimus' crew.
seeing as to how bay doesn't like beast-formers whatsoever, I doubt grimlock will be in it anytime soon.