Okay, first let me say: as of now, they're only doing three movies!
Now that I've got that out of my system; there's no way they could kill Will off as 'minor' character. I mean, if they thought there was no other way to do the films, they might kill him, but not because of budget cuts. Too many people like him, and he's too vital to the story. (Not to mention the obsessors like me who are infuriated at stuff like this... no offense)