The nexus 10 wasn't even rumoured until a couple days ago. I'm sure work on this started before that.

It looks like this is for testing key components on a tablet platform, not something that will be promoted to end users (yet). For that, it makes sense to aim for a device that's already out there and has sold well.

Or, as the post puts it: "To be clear, this is not going to be a tablet Unity interface ... we can ensure pieces such as the kernel, power management and other related areas are working effectively on a tablet device."

If the Nexus 10 is sticking with Tegra apus, the Wayne series won't be out until next year, so if they target an xmas release on the Nexus 10 then they are still stuck on the same Tegra 3 (probably overclocked).

The Nexus 10 will run on the new A15 Exynos chip (5250?) with a Mali T-604 GPU - same as the new Chromebook