Technically, Kojima was done with Metal Gear after the first one. But his former collegues convinced him to make MG2 Solid Snake, and it was a masterpiece.
Later, when he said that he was gonna pass the rod to his team for MGS4, he received death threat from angry fans, which provided incentive to continue directing.
So, not only this has already happened to Metal Gear, it will happen again, cause it's standard policy for mangas, animes, movies and videogames since the 80s.
There is no compelling reason for Konami, or any big game company out there not to stretch a popular franchise and squeeze it dry with Hollywood-style sequelitis.
Now on topic: armored Vamp wielding a freaking hi-frequency blade while battling Raiden on top of a moving train. Wait, what?