IMHO, Nokia has to give up on Maemo/Moblin, keep Symbian (but fix it, please) for low-end smartphones (because in a couple years that's the only kind of phone there will be) and adopt Android on the high-end smartphone line and differentiate on hardware (theirs has always been excellent). Maemo/Moblin is going nowhere fast and there is no space for more OSs in this space right now.
If they can fix Symbian and make cheap smartphones that are feature-competitive with Androids, they can also bypass telcos and sell direct to customers.
But that's just my advice. It's unlikely he will follow it.