It's true that we're going on six years since the last mainline entry to Halo; however, 343 scrapped their development with Infinite somewhere mid-progress as they realized they needed to build a new engine to accomplish everything they wanted to do with the game. So yes 6 years is plenty of time to make a game, but starting over to build a completely new engine does take time. A lot of posters keep bringing up how embarrassing it is that the xbox hasn't released a big exclusive for the system, which I can agree with to a degree, but it would be even more embarrassing if they had released Infinite before it was ready and the only exclusive launched thus far was a bomb - Halo no less. The PR would have been catastrophic. Instead, the only people completely up in arms about it are die-hard gamers. The general public doesn't even know any better.