I asked this question myself... In a few years there just has to be a better model right?
I can live with a 600 if I need to... But what really disturbs me is that Sony put some firmware protection in so that you can't put custom hacks in the new gen... This is bad news... Once I learned that my 505 became much, much more valuable to me and I am considering buying a backup.
In the meantime I handle it like a faberge egg and keep it under plastic!