If they kept with Snake adventures the next game would probably be shit.
I think he will come back (Kojima not Payton) maybe not for MGS5 but for some MGS.
I think maybe Kojima needs to let the team fly, he basically ""raised"" them and he needs to atleast give them a chance to make something new. MGS needs a new start, Kojima leaving may just be the break. Or, MGS5 can be shit.