You won't have to wait for the Rockchip SoC to get a handle on Silvermont versus ARM on a TSMC 28nm process -- the Intel SoFIA chips already announced and slated for shipment later this year (dual core) and early next year (quad core) will tell the same story. That's why Intel could work this deal with Rockchip -- they already had ported Silvermont to the TSMC process.
When I saw the title, I assumed this was Intel's way to get into ARM without losing face. But... no. It's Atom. They just won't give up on x86. Sorry Intel, nobody wants it, execpt for the few thousand Win8 tablets getting churned out every month.