As long as the market share of any newcomer is low enough, Google can leave them out in the cold for app support (or intentionally interfere by blocking YouTube access, similar to what they did with Windows Mobile, and now Amazon's Echo and Fire platforms), and they'll die off for that reason alone.
Whether it's an Android fork or a new OS like Tizen or some new Windows flavor, it won't beat Google unless it has the market share to force Google to support it with apps. And it's hard to get that market share without Google's support.