There is plenty of competition, some of it pretty cut-throat, between vendors of Android phones. That's what keeps driving the prices down and the specs up.
Android is open source so we're also reasonably well-insulated from anything happening to Google. Yes, most manufacturers pay to have access to the Google apps but there are drop-in replacements for nearly all of them. I think Maps and Hangouts and, of course, the Play Store, are the only ones I use.
The biggest risk to consumers is the age-old problem of a monoculture. If it goes too far this can stifle innovation. It can also magnify any security risks. Having the OS open source does go some way to mitigating this as the source code is available for research. But as the OpenSSL debacle demonstrated there's no guarantee of that.