Grabbed a Nexus 5 myself, because hey, it's pretty hard to beat for $300 and also because of it's tight integration with Google service, with which I myself am tightly integrated.
But, for my mother? She couldn't give a damn less, which is where I think a lot of these smaller manufacturer's will succeed. I actually quite like the idea of a simplified/dumbed-down Android experience that Xiaomi is offering and would seriously consider it for my mother and less tech inclined friends/relatives.
A 30 year progression has brought that old dream to hundreds of millions, who just call it a "phone."
I have a hard time seeing the long history in terms of just one brand, or even a few. The trend is much bigger.
I actually like the confusion of the Android market, but I chose a purely conforming Nexus for myself.
Still I like an ecosystem that is really that, and Xiaomi contributes to diversity, even if I don't buy one.