People are not only now thinking of a Spider-Man sequel. It's been fairly obvious that they started developing the sequel the moment they finished the first one.
Also, Insomniac is a big game developer with several studios that are working on several games at the same time. They are soon releasing Stormland for Oculus for example...
I find it ironic that the only Xbox exclusives that caught my eye besides Halo and KI were ReCore (Made by Kenji Inafune, a Japanese man) and Sunset Overdrive which was made by an ex Sony developer. Step your exclusive title game up, MS. Lol