Today Koen gave me link to one discussion on Maemo-devel mailing list. It was about end of support for Nokia770.
Thread is interesting — some guys from Nokia wrote that this does not mean end but in same post write that there will be no new OS releases for 770. Hacker edition of OS2007 for 770 is also mentioned as solution but this is unofficial and unsupported (it works quite good on my device).
I think that Nokia770 is another device which will go into trashland due to fact that no one work on building external images for it. Ok, OpenEmbedded can build software for it but flasher is closed source and I do not know does format of flash images is published somewhere.
And some parts of Nokia rootfs are closed source too..