Yes you are right, it make a OpenNextUri, I tough it wasn't working because I've tried only with rygel (report Invalid action http://api.wamp.ws/error#generic). But now I've tried with foobar and there it works as expected, any idea on why didn't work with rygel?
I've also tried the dbus api with rendererconsole.py and there if I do a open_next_uri() on rygel renderer the item start playing directly without waiting the end of current item...
And patches are welcome ;-)
I'm not a very experimented programmer (more hardware guy...) but if I write some not too dirty usefull code I will try to submit it :)