Tizen will be the main competitor to Android. Other companies tried to compete but lacked the hardware necessary to do so. Samsung has what it takes to make it successful. Android's success is not from Android itself but from the hardware it runs. Samsung has the hardware volume and market share to make Tizen successful and be adopted by other manufactures. Windows Phone, Blackberry and Webos lacked the hardware to properly compete. Apple will soon struggle to compete due a lack of volume.
The future is Tizen!