Where'd you read this? Atom is an ARM competitor. Intel wants you to believe that it's a universally superior option that, in its lowest power incarnations, is suitable for phones and other mobile devices. Including an ARM core on-die would be a complete contradiction of this market position and I doubt Intel would do that.
You guys are comparing netbook or nettop Atom solutions, Moorestown probably tends to draw around 2W or less so it's more in the same power class as the OMAP3 used in the Pandora. Unfortunately, it's a three chip solution (Lincroft + Langwell + PMIC instead of OMAP + TI PMIC/audio/whatever) and as far as I can tell there's no package on package support for stacking RAM on top of Lincroft, so it'll take up way more board area. And compared to the dual core Cortex-A9 SoCs available now (Tegra 2) and next year (OMAP4, Orion, U8500, and others) you probably won't see dual-core in the low power Atom cores (currently Lincroft in Moorestown and Pine Trail, then whatever they use in Cedar Trail/Cedar View). There's Hyperthreading instead, but that only does so much in comparison.
IMO an Atom Pandora would be an especially bad idea precisely because you'd lose software compatibility with the Pandora library and people would have to release dual binaries (or a dual mode binary format would have to be made I guess), and it'd be a much greater burden on the OP team to support both for their own software. You'd see a lot of things that'd be ARM Pandora only or x86 Pandora only because of strong ISA dependence in the code; lots of emulators will have ISA dependence for instance.