According to the blog "The Really Mobile Project" Nokia is going to replace Symbian with Maemo on the high-end smartphones.
While Maemo looks quite cool I think this isn't the end of Symbian. Instead it might become the end for S40 since my guess is that Nokia will start to use Symbian for mid-range and - in the long term - for low-end phones. (Although I don't expect it to power ultra-low-cost phones like the 2330 anytime soon.) Both market segments are not suitable for a heavy-weight like Maemo.
This makes a lot of sense since Nokia invested a lot of money into the platform and Symbian might be much more future-prove than the proprietary S40 platform.
Beside that Symbian (S60) is still one of the best platforms to run J2ME on.
Maemo: It will have to compete with Android and iPhone. I don't know if it will really gain momentum.
But only time will tell.