Without Samsung's manufacturing and marketing capabilities, Android would have died long ago. Without Samsung, every other Android OEM manufacturer is a profitless midget, to put it mildly, including Google's own Motorola. In other words, Samsung controls the market with its monopoly manufacturing and marketing capabilities, and whichever way Samsung goes is the way the market will also go. Samsung's manufacturing and marketing capabilties simply overpower those of any competitor. As Tim Cook said in his NBC interview with Brian Williams, the actual knowledge and expertise to produce consumer electronics on a large-scale has simply left America's shores forever and is concentrated in Asia, which today largely means Samsung (but the Chinese are catching up and are just a few years behind, as Samsung itself recently warned). Apple is trying to separate from Samsung but finding it extremely difficult. Google has helped sow the seeds of its own destruction in creating this creature called Samsung who, for its own business reasons now, has to steal and co-opt via Tizen the entire Android app ecosystem from Google in order to drive its own move into software and services on its path to becoming a half-trillion dollar company. Android developers will just offer their apps without any modifications on the Samsung Play Store. Samsung's Android hardware is getting squeezed from below by Huawei and ZTE and at the top from the iPhone and X-Phone who all foster and enjoy their own ecosystems. Having one's own ecosystem guarantees one's long-term viability much better than selling commodity Android hardware alone. So both Samsung and Google want to "go Apple" and have their own complete ecosystems with hardware + software + services, which is actually just the IBM model of Palmisano over the past decade that even convinced Warren Buffett to invest over $10 billion in IBM.
Samsung has already tested and/or demonstrated Tizen on the Galaxy S3 and S2, so putting it on the Galaxy S4 is merely the next step. They'll actually flood the market with Tizen phones from the high-end to the low-end at every price point, which has been Samsung's "human wave" strategy before on both feature phones and Android phones. It won't be a half-hearted attempt focused on just low-to-mid-level phones, which is naive and wishful thinking. The first Tizen phone will be a high-end, not low-end, phone announced at the Mobile World Congress in Barcelona next week. Piggybacking on the already-successful Galaxy line will be the quickest, most effective way to introduce Tizen to the masses on a mass scale, which is Samsung's objective. Samsung will promote Tizen on the Galaxy S4 as "Android Plus" because it'll run all Android apps flawlessly and offer widgets just as the S3 does plus offer incredible new HTML5 app capabilities that will blow everyone away once Samsung reveals them to the world.