ABI Research has released a new report called "Mobile Linux", where they, unsurprisingly, predict that Linux is going to grow immensely in the mobile space during the next five years. Linux will be used both in smartphones and as an RTOS replacement in mid-tier phones.
The evolution of Linux on mobile devices seems to follow the same path as Linux on the desktop: it started out fragmented, with lots of separate bits and pieces, but is now in the phase where these components are either being replaced or compiled into complete solutions, just like gtk/gnome and qt/kde have unified the X desktop. Of course, there are still two different desktop environments, but I'm not sure if that's a disadvantage. The competition should keep the developers of the respective systems on their toes. It seems likely that there will be a similar division on the mobile side, between gtk and qt(optia), and possibly also some proprietary alternatives. With projects such as OpenMoko, there's no need for a phone manufacturer to build everything from scratch anymore. The basic components, including apps, will be there, and all they'll have to do is to customize the platform and add the stuff that makes their devices different from the competitors' offerings.