Doesn't the combination of Google+ Sign-In and Google Wallet remind you of Microsoft Passport[1]? I wonder if people who had concerns over a decade ago, will have the same concerns now.
Except that Passport was embedded in the OS. And if I remember correctly, a royal PITA to set up with multiple accounts, or manage your existing data. I infinitely prefer this to be part of the internet instead of the OS, where it's easier to support multiple simultaneous logins.
But not in Windows, OSX, or Linux, where Chrome runs as an application. And it's likely to be embedded (like the normal Google account embedding) in stock Android devices, but not some forks or some carrier modifications (since Google accounts aren't required for any of the features any more).
The same cannot be said for Windows. Especially when Windows held an overwhelming monopoly on desktops, unlike Android.
android is going to get an overwhelming majority too. Pretty soon even the basic $30 phone is going to be a smartphone likely running android. iPhones are going to keep on growing at a healthy rate but their numbers will dwarf against android.
[1] https://en.wikipedia.org/wiki/Microsoft_account#History