The CyanogenMod team has been hard at work building CM10.1 for various devices over the last several weeks, with new devices getting official builds almost daily. Yesterday, we saw 10.1 hit AT&T and T-Mobile's versions of the Galaxy Note and AT&T's S II Skyrocket; today, the first nightly just landed for T-Mo's Galaxy S II, as well.
The device, codenamed Hercules, differs from the rest of the S II family, as it has a Qualcomm processor instead of the Exynos of the other variants. This is likely the reason that it is getting 10.1 builds, while most of the others are stuck on 10, or even 7.
As always, if you plan on flashing this, don't forget to grab the latest Gapps.