There's always room for something new, no matter it wins the market or not. Yes, big fishes like Apple, if they make a little change in the homescreen, that'll boost a lot of sells. Because they are already established. That doesn't necessarily mean that they'll (Android or iOS) be holding the positions forever.
What Ubuntu Phone OS is, is completely different that the other big players. Even though I'm skeptical about their marketing strategy and doubtful whether they'll succeed or not, the concept that they're working with is what it should be with technologies. Users can't learn Windows 7 at office, and XP at home, and later Ubuntu at a friend's home, and Windows 8 when the office adopts it. And in the mobile, they just can't also learn iOS, Android, FirefoxOS and more. Even if they're learning, the two just don't match. Yes, Android and iOS -- they've understood that one OS should be everywhere -- so we get the same OS in a tablet and smartphone. Why not in Desktops then ?
I think Ubuntu is trying to do that in a much prettier way. And the Dash -- yes, it has its own algorithmic problems and time lags, but as they continue developing it -- it is truly a big step in the future of intuitive computing.
I would like to see 'em succeed with it.