It has now been independently confirmed by multiple sources that due to shortage of Samsung's dual-core Exynos processor, which was planned to power the entire Galaxy S2 line, nVidia's Tegra 2 processor will be powering some of the devices. It's not certain at this time how the production will be divided up, but it's expected that certain regions will get Tegra-powered Galaxy S2 devices, and others will receive the Exynos-powered devices. Ultimately, though, both chips are very powerful, and performance between the two seems to be comparable, based on reports thus far. More news as it develops.
[via Engadget, ITProPortal]