As for Apple gaining market share in the US, I think what we've seen is that Android is starting to run out of feature phones to replace, so it's now in a fight for the high end space with Apple, which will probably see movement in both directions for a while. I suspect a significant portion of the iPhone market and a larger portion of the Android market is really just phones with touch screens -- these are people who don't buy apps or use most of their phones' capabilities. The "network" effects that will determine the fates of the ecosystems depend on people using their phones as computers rather than merely phones.
In Europe recently Windows phone (i.e. Nokia) is doing very well. It will be interesting to see how that plays out too.
http://9to5mac.com/2013/10/04/comscore-apple-gains-on-androi...
https://twitter.com/asymco/status/386207186801917952/photo/1
They just released a new iPhone. It's probably fair to say that that will be a short-term bump that will flatten in good time.
I think it's seriously disingenuous to describe the 5C as a "serious downmarket move". It's a token move at best, and doesn't get anywhere near the price point a "downmarket" device would require.