If they play their cards right it wont be a .0001% . We need an OS out of the clutches of microsoft, google and apple,from somebody we trust more with our personal data . So far Firefox is the Mr. Clean and that is a brand image it has worldwide . Also using a standard compliant language (html) for development they will attract a lot of developers as learning curve may be small ( I hope so) .
RIM recognized the need for momentum with apps when they started designing QNX based blackberry OS but they chose the alternative of android emulation i guess. But somehow i feel that choice of Mozilla is better .
With Regards to Bada Tizen et al , i dont think anybody other than avid tech readers may have heard of them however good they may be . But even a layman may be willing to try something from makers of firefox . Branding is what makes selling a tad lot easier . And if quality is good people should stick .