Personally, I am sad that they quietly dumped the OS after promoting and trying sell with so many ads & stuff. But then, its Samsung, what else to expect.
Tizen devices may suffer because of the previous treatment meted to Bada eco-system as well.
Like Ubuntu? Not sure if they will be able to support all the apps & the performance will be good. It has to be, because an average performance of Android OS on BB10 did not seem to helped them much. Though, it might be also due to ridiculous pricing...
Not sure of the technicalities but Samsung is in a position now to get the main developers to port their apps to Tizen platform so that they work better natively. They were not in such a strong position back when they were selling Bada devices. I do not think Samsung would have a hard time selling enough Tizen devices to get it above Windows Phone's market share globally.
Tizen share above Windows Phone? How?
Already some operators who had promised support for Tizen has backed out. Tizen is not going to launch in Europe/US market, meaning Samsung knows that these markets are well aware of Phone OS. And was Samsung successful with their latest Galaxy S5 over LG G2 or HTC One or Sony Z1? If not, then it means brand Samsung is also going down.
Then how could Samsung succeed with Tizen?
Just price them competitively and make all major Android apps available on it. It has to be that simple. People do not care about the OS on their phones. Tizen already looks like a copycat of TouchWiz Android... If they can get an app store with all the popular apps, it would be just fine for the company. I am not saying it would happen immediately but it should not be that big of a deal. Samsung has a brand value and people are willing to buy their shitty devices at insane prices.