Tizen, aka Bada and Meego (aka Maemo and Moblin), seems to be formed out of a bunch of dead operating systems, in the hope that if they combine all of them together, they could create a killer product. But in the words of Google's Vic Gundotra: "Two turkeys don't make an eagle", or rather in this case "four" failed operating systems don't make a successful OS.
Samsung plans to release a high-end phone with Tizen this year, in August or September, which seems to be placed between a Galaxy S4 launch in US, and a Galaxy Note 3 launch. Samsung hasn't tried to put one of its own operating systems on a high-end device yet, so this will be a first. I understand why they are doing it, though. They want to have a real alternative to Android (WP8 hasn't been that for them), and they want to have full control over it, and decide the direction for it.
Unfortunately for Samsung, though, so far I've seen no evidence of a single company succeeding with its own OS, besides Apple. And Apple only managed to do it because they were the ones to start the whole touchscreen smartphone revolution, and because of many other factors and reasons for which people love Apple and are loyal to them. But imagine if we were all using the Android devices we're having today, and the market would be so saturated with it, and Apple would release iOS for the first time today.
Even if it would be as "advanced" as iOS 6 is today, and not just launch iOS 1.0 the way it was in 2007, it wouldn't be anywhere near as successful. It would be seen as a me-too kind of product, with no real advantages over Android, and without years of branding they've built for the iPhones so far. It would be dead on arrival, pretty much.
Samsung is a lot less recognized as a premium mobile company as Apple, yet they think they can pull this off? No other OS so far has succeed since iOS and Android, and Android only succeeded because it allowed all manufacturers to use it, and created a strong enough ecosystem to compete with the iOS ones. But even after all these years, developers are still mainly preferring iOS. So if you already think Android is a "second rate" OS (some still do), then Tizen will be seen as a "third rate" OS, or worse. How can it possibly succeed then?
But let's entertain the idea that Tizen will be widely successful for a moment. At the very worst for Android, they'd still keep the Galaxy S and Galaxy Note brands (with Android). They would be crazy to switch Galaxy S and Note to Tizen, and trick consumers into buying it just because they have the same names. Apple got a lot of flack for even changing the Maps app, which is just one app, and then nobody used it anymore and turned back to Google Maps. Imagine the level of outrage if Samsung removed a whole OS behind Galaxy S and Galaxy Note. It's crazy to even think about it, let alone actually do it.
What they would do is try to develop a similar line with the Galaxy S, but with Tizen, just like they tried with the Ativ S for WP8 (and so far they've failed to gain many sales). This also brings me to another point. If they will ever be even remotely successful with their Tizen devices (say 2-3% of the smartphone market, for Samsung Tizen devices alone), I give it a few quarters before they completely drop support for WP8. Samsung will simply have no use for it anymore, and they've only ever used it as a stop-gap until Tizen was ready, and to have something to use against Google in negotiations. If Tizen is more successful than their WP8 devices (shouldn't be very hard), there will be no reason for them to support WP8 anymore.
But again, this is making a very big assumption that Tizen will be successful. I still believe that is still very unlikely, considering no other modern OS has become successful after the multi-manufacturer OS that is Android. Maemo failed, Meego failed, Bada failed, webOS failed, WP8 and BB10 are failing. There's not one example of any other OS even coming close to succeeding after iOS and Android. So whoever thinks gaining a lot of momentum with Tizen should be a breeze for Samsung, is going to be very disappointed a year from now.