It's tempting to read the "macOS" rebranding as some grand statement about the Mac, but, truth be told, "Sierra" is more indicative of what we're getting. The name comes from a mountain range that encompasses Yosemite and El Capitan rather than moving away from them. It's another year of building on Yosemite's foundation, another year of incremental change, and another year of over-saturated mountain wallpapers.
Like El Capitan before it, Sierra focuses on a few marquee features, a couple of under-the-hood changes, a smattering of smaller tweaks, and one or two signposts pointing toward future development. It's the next release of OS X, new name or not. And we've spent a week with the first developer beta to dig into some of the new features ahead of the public beta in July and the public release in the fall.