Not only is the Nokia N8 the first Nseries smartphone to run the new Symbian^3 OS, it's also going to be the last. After the N8, all Nokia N-Series smartphones are to run on the new MeeGo OS, according to Gizmodo.
MeeGo is a fusion of Mameo (which was the Nokia N900's OS) and Moblin, a Linux-based mobile OS developed by Intel. Nokia and Intel unveiled MeeGo at this year's Mobile World Congress back in February. Nokia spokesperson Doug Dawson has confirmed that "going forward, Nseries devices will be based on MeeGo."
A separate press announcement from Nokia says that MeeGo will bring "a wealth of Internet, computing and communication experiences with deep Ovi service integration." Hopefully this will mean a platform that can potentially rival Apple's App Store and the Android Market in terms of access to apps and internet services.
Symbian will continue to exist on lower-end Nokia, Sony Ericsson and Samsung handsets, but as far as the Nokia Nseries is concerned it's out of the game.
Update: We've just heard from the Symbian Foundation that, while it's going to be MeeGo for the Nseries from now on, it's not exactly curtains for Symbian smartphones. All forthcoming Nokia Xseries, Cseries and Eseries smartphones will continue to be Symbian-based.
The Nokia N8, the last of the Nseries Symbian smartphones, is due for release in August.