I saw that title of this topic, and where on earth did that video say just 8v8 gameplay, sure its more likely, but they never ruled it out.
Secondly, to your forge ideas, some terrain should be included, like with a bigger forge world, with maybe a plains that turns to a desert like area, a snowy mountain that connects to a forest. But things like space, wastelands, mars and swampy will almost never be in the new trilogy, because firstly. Space, that would be too hard to create a safe environment to forge in, Mars, even though in the books mars is important to the UNSC, we have never been to it, and i doubt we will. Swampy, sure if there are missions like 343 Guilty Spark from Halo CE, but otherwise it wouldn't make sense to include it.
But i do agree that the just grass theme is incredibly boring on Reach, though its still fun