the problem is that movies, unless they're based off a novel or play or something, aren't made that way. Sony has an idea of where they want to take the franchize, but it's an idea that could change significantly in the next few years before AMS 3 is written. The idea they're saving it is just not realistic. Look at Star Wars for example, George Lucas and Kurtz had an idea where they wanted the series to go, but in 78 they came up with making Darth Vader Lukes father. This made Jedi an entirely different movie than if they left Luke's fathers ghost in the script of Empire. Not to mention how poor of a decision it was to harm a movie by holding something back to you can stretch it out over the span of several films.