Is there a future in Symbian development

Mobile games is already a very competitive area. I assume there is still room for new players but you can only succeed with top quality products, not "just average" games and a good exposure (which is easy with good software).

Linux definitely has a future - especially in China and Japan where it has been selected as one of the two reference platform (with Symbian OS) by NTT Docomo). I don't know a single phone manufacturer which does not have some interest in Linux... but Linux is currently lacking a kind of standard embedded applicative framework. Qtopia is one of the competitor but is relatively expensive. So, if you are already afraid of all differences between different flavors of Symbian phones, just wait for Linux 

Regarding Symbian platform, there is still some work to do but it is not because millions of phones based on this platform are selling that people are buying millions of softwares.... so I assume that several companies are just reconsidering the cost of developping for this platform compared to probably disappointing sales for "just-average" applications.