All companies do that and im mainly gonna wait awhile for the successor after what happened with 360s beginning, yes ms admits it wont be another rrod fiasco but launch systems usually break down after so many years due to the fact it uses an old version of the gpu/ cpu, while 5 years later, they use a better, more efficient version and dont sound like an effing jet.
GT: Yami Anubis X I believe that is it 3DS FC:1891-1173-7323 Name YamiAnubiX
It's up to Microsoft when they release their next console, and since they haven't even announced it yet, I don't think we will be able to play on a next-gen Xbox until 2014 or late 2013. (By that I mean if the console gets released 2013/2014.) (That's if they announce it this year or next.)
So Halo 5 could be this gen, but at the very end of this gen. Or a next-gen title, but maybe not a launch title.