Beside the April fools day N9 looks like an accurate name for the next MeeGo device as Nokia said it will change its naming strategy to only one letter and number following by the year of production (just like the car industry is doing). Already done with the Nokia X series and the Nokia C series

So the leaked flagship Symbian device is named N8. Probably N8 (2010) with the next years version called N8 (2011).
I believe the upcoming MeeGo Device will be named N9 (2010). And the one coming next year N9 (2011) etc.