It revealed a major concern of Nokia in either continuing to support, or not, its main mobile operating system - the Symbian OS.
The seemingly "brutally honest 'burning platform' memo" basically informed its employees of the already-known market changes brought about by the Apple products and ecosystem. Add to that how support for Google's Android is eating up Symbian. The message forebodes of upcoming changes within Nokia.
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I don't think its anymore a question of "to jump or not to jump" for Nokia, but when to jump.