This is kind of like how I thought halo 4 would be.
When I started thinking up ideas for Halo 4 a while back, I was like
Master chief explores mysterious forerunner ruins and solves Metroid-Prime like puzzles to advance while simultaneously fighting the Flood.
Brutes get pissed (they're sore losers) and want revenge; another invasion of Earth. With Chief gone, humanity's last hope is their Sangheili allies. The Arbiter and the Elites help defend Earth.
And you switch off between the Arbiter and the Chief like in Halo 2.
For better or for worse, it looks like Halo 4 is going to focus only on Chief and the forerunners.
hopefully, would be a good direction for the series to go
I've got mixed feelings about this.
I personally think a really good direction for the series to go would be 150,000 years into the past, during the Human-Forerunner War.
That way, it will be much easier to flesh out the Forerunners, mostly because there will be living Forerunners. We can also get a feel for humanity's more advanced technology during that time. But most of all, we can return to the classic Halo formula:Humans. Aliens. Flood.
I would center the Humans around magnetic-based weaponry (gauss carbine, railgun-type sniper rifle, etc) for aesthetic reasons and because.... well..... its a different direction. It's more advanced that chemical-based firearms, and less alien-looking than plasma and light-based weaponry. It's very futuristic, but still has a distinctly human feel.