Re: three of top five...
That's a fair point but taken in the round it's worse news for Samsung than Apple.
Whatever the relative merits of iOS and Android, if anyone wants iOS they can only but it from Apple. The closest Samsung has is Touch-Wiz, which doesn't have the same draw as it's tied to Android and increasingly Google services.
Samsung are going to get eaten by the rise of the Chinese more than Apple because their point of distinction is so less defined or embedded. I expect Apple will continue a steady decline and settle at 8-10%, but I can't see where Samsung will settle.
It's a more or less perfect copy of the PC world with Apple using (often purely emotional) pulls and selling standard kit at margins Wintel vendors can only dream of - Nice work if you can get it.
Strategically, if they wanted to be a major long term player in the phone market, Samsung should have stuck with Tizen and gritted it out.