6th
Looks like Flash 10.1 could provide the first cross platform environment that will enable developers to write applications for pretty much all smart mobiles and PC web browsers using the latest version of Adobe Flash Professional CS5
Flash 10.1 applications will run on smart mobiles based on Windows Mobile, PalmOS, Android, Symbian, Blackberry and iPhone*; as well as not-so-mobile PC web browsers. (From here.)
*Well, not quite. Looks like iPhone users won’t be able to freely enjoy Flash applications nilly-willy. Developers will have to generate iPhone specific builds of their Flash apps which I presume will have to go through Apple’s App Store. (More info here.)