Disclaimer: Mostly based off of common knowledge and opinion.

If you haven't noticed recently, Samsung is everywhere. And not just Samsung Mobile. There's more than 10 other departments run by Samsung.
ex. Appliances such as refrigerators, washing machines, television, dryers, etc...

And now it's onto taking on it's own provider. Google had taken control over Android a while ago. And since then, many companies have manufactured phones, tablets, and laptops using Android (not really laptops though).
Motorola (now owned ny Google), HTC, Amazon, and most importantly, Samsung.
Google has always been with Samsung, and even alongside the patent wars a while ago against Apple. Since Android is such an open source, typically anyone can barge on in and configure it to their liking. Have you seen Facebook Home recently?
If you haven't noticed, Sammy has claimed fame with it's "Galaxy" devices usually providing the top specs in their flagship phones. And using what OS?
Oh that's right, Android! (with a Touchwiz skin)

Here's the thing. Have you seen a TON of Nexus' (Nexi?) around. I've seen them, and heard of them. But just not as much as I've seen Galaxy phones. They've made Android famous, but not as Android. I've had my S3 for a while now and all I want to say is that my next phone will be a Nexus. I can't stand Touchwiz and Samsung bloatware. As much as I loved it as my first smartphone. I got bored, because Android fan boys like me aren't new to it anymore and won't need anymore 'coaching' from Samsung.

The verdict: Samsung has Google tied up. They've let their leash on Sam too long and now there's nothing they can do. Sure, someday, Google could man up and say, "Hey, you're getting too popular, we're cutting you off." And not let them use the OS anymore. But, what most people are guessing will happen is that Samsung will respond by creating their own OS to take on Android entirely. And they could win. They're percentage of devices sold has gained over 20% since 2011. It's still everlasting.

"When Samsung’s Galaxy S4 gobbles up even more Android marketshare, Google is going to have little choice but to roll out the red carpet. Galaxy has completely overtaken the Droid brand, and is now the public face of Android. Samsung is going to continue to crush other Android OEMs and Google cannot do anything about it. We may see less innovation in the smartphone market as the dominant players feel less pressure to take risks.

Whatever Samsung wants, Samsung gets, and everyone else can have the scraps." (Source: ExtremeTech)

I have a lot more to say about this, but anything more would bore you. Thanks for reading!

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Other Related Links:
-Samsung Clones The Play Store From Google
-Google Worried By Samsung's Dominance