How to continue after a trilogy.

It's rare that a movie franchise would go on after a trilogy but to make each film just as great or better seems challenging. Now with the potential of Andrew Garfield not continuing in the role after part 3, where does that leave with the direction of Spider-Man? will they do a spin off or try a another Spider movie with another actor? That would be hard since Andrew is singing for a three film hero deal and then to go with another person would, in my opinion, may not sit well. Maybe if they do an alternate world or spiderman 2099 or ultimate spider man as a continuance may work. Depends on where they want to take the character. that also still leaves the question of villains. since it looks they are doing a sinister six involvement, would either part 3 o4 be open to a venom encounter or someone else entirely.