UPDATE2: Qualcomm Snapdragon uses the "Scorpion CPU", a Qualcomm derivate of the ARM Cortex A8. (thank you alxlr8!)
While Nvidia Ion is "only" providing graphics acceleration to netbooks and nettops, the new Nvidia Tegra 2 is supposed to be the first Nvidia SoC (System on a Chip) implementing both the core CPU and GPU functionality for netbooks/smartbooks.
According to Xbitlabs, Nvidia is going to make a major announcement during next CES (Jan 2010): the first netbooks/smartbooks with Nvidia Tegra 2 are going to be launched already in 2010.
Very few details are available: it will be a dual core processor with 40nm technology.
As you may remember the Nvidia Tegra 1 (used in Microsoft Zune HD player) implements a single core
The new ARM Cortex processors are used in other ARM SoC targeting netbooks/smartbooks, for example the Qualcom Snapdragon (actually a Qualcomm derivate called Scorpion CPU).
For this reason I guess that Tegra 2 will also use the dual core Cortex A9 MPcore, the max CPU clock should be at most 2GHz. Of course this is a maximum clock, the clock used in Tegra 2 the can be much lower.
2GHz seems to be the maximum clock possible at 40nm for these two processors: in recent press announcements Synopsis presented a 2GHz ARM Cortex A8 core and ARM a 2GHz Cortex A9 core, both using a 40nm geometry.
Of course Nvidia Tegra 2 based netbooks/smartbooks can only run Linux variant: a distribution or at most Android/Chrome OS