First of all the answer. Impossible!
This started with a recent article from ARCchart which says that Nokia could use Linux ( like Palm will do in the future with their handhelds ) for the Series60 platform.
The main reason for this was that Nokia, even if it owns about 50% of Symbian Ltd, pays a 5$ license on every phone sold with Symbian OS. This 5$ fee is insignificant thinking that the other parts of a Series60 phone usually cost way over 100$.
Another reason was that Nokia has developed the Nokia 770 tablet on Linux instead of Symbian OS. The reason why Nokia did this is because Linux is better for this job. Nokia 770 is not even a phone. Is a totally different gadget. For such a device Linux is a big advantage because with a small effort they will port open-source programs to Nokia 770's proprietary Linux.
I find the migration, for Nokia's Series60, impossible because Nokia is just doing a great job with Series60 now. They have 75% of the SmartPhone market. This shows that this Symbian OS - Nokia formula is a great one and Nokia does not want to lose it's market share with such a switch