The majority of them are Linux-based, and all of them make heavy use of the same web technologies for the primary part of the user experience. The exception is WinMo, but I can't believe that they're going to last long at all with IE7 as their browser of choice. They're going to need to either light a fire under the IE9 team and somehow get feature parity with mobile Webkit, or just throw in the towel and allow one of the other browsers on WinMo.
And as for the suggestion that Apple is going to take over... RIM still has the largest market share in the US. Apple is a niche player, and they always will be because of the premium they charge on their hardware (now further compounded by the restrictions imposed on their hardware.)
With WinMo 7 all apps must be coded in Silverlight, and there is no native development. This might be okay if they weren't using IE7 as the basis for the WinMo 7 browser.
And as for the suggestion that Apple is going to take over... RIM still has the largest market share in the US. Apple is a niche player, and they always will be because of the premium they charge on their hardware (now further compounded by the restrictions imposed on their hardware.)