"Hey, don't buy our new system, we're fine if you don't" sounds like an awesome way to move units. With Halo moved away from launch and considering the reveal was pretty middle of the road, it seems like Microsoft is trying to manage expectations, which may be a smart move depending on if the console is super expensive. If either machine is priced above $450 at most, they're not gonna move the kind of units they need to move to justify the expense. They really needed Halo to look mind-blowing and stoke people up with that gotta have it feeling, but it looked like a current-gen game for the most part (partly due to their shitty stream, it looked better when Digital Foundry took a closer look at it).
It's gonna come down to library and price, just like it always has, and more importantly -- what Sony does. The next generation is Sony's to lose imo.