Could I have any sources of Symbian replacing S40 as Justin Lee mentioned? According to the interview question and answer with Jo Harlow, head of smartphones at Nokia, S40, Symbian and Meego will all exist catering to different markets (Source: http://www.knowyourmobile.com/blog/420018/mwc_nokias_jo_harlow_talks_symbian3.html)

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Is Series 60 predicted to move down the range to supplement S40?
The role of Symbian is to take services and other experiences to the mass market, The role of Series 40 is particularly important for the emerging markets and in the low-end where Symbian can’t achieve to bring the internet to everyone but in a more affordable, more accessible type of experience.

So the idea is not that Symbian will replace S40 but they both play their role.
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The best way to picture it would be from the graphic in this post: http://nokiaexperts.com/articleimages/2010/02/nokia-strategy.png (Source: http://nokiaexperts.com/symbian-s60-s40-meego-nokias-strategy/)