Has Nokia ever asked you to pay for an update? No. Do you have to pay to get a new version of the OS from Nokia (whether it's named Maemo 6, MeeGo or Grobelsnock doesn't matter)? No.
Besides Nokia really should expect some flak with their announcement of Meego.. they have announced the end of Maemo.. with, as yet, no reassurance that current N900 owners are ever going to enjoy the full potential of the device they have shelled out top dollar for. I would be concerned.