It's possible, and has been discussed previously. So far as I know, no one is working on such a project though.

Most likely, if a Symbian port ever does happen, it will be after that OS becomes fully open source. However, by that point, the next Maemo device will be out, the N800 and N810 will be growing old, and therefore, interest in developing such a port is likely to be small and dwindling.