I don't see it making a huge dent in Android or iOS for a while, but it's not intending to as initial releases seem to be concentrating on the Latin American market where neither of the other mobile OS's have a solid grip. Seeing as it allows more user control than iOS without some of the complexity that android can bring, plus being HTML5 based, it should
do well due to it's main competition being low-end Android devices, or feature phones. Hopefully the OS will bring an improvement in HTML5 programming which will increase the strength of the the platform and subsequently a fair shot of taking a significant market share, though Ubuntu touch will be looking for some market share too. It may have the weight of Mozilla behind it, but Bada was a Samsung pet project that ended up marginalised despite their backing so it's hard to call really, and ultimately will be a case of 'wait and see'.