Drafts is one of many apps making the upgrade to iOS 7 today, but in this case, it's going all the way.
Drafts 3.5 will only support iOS 7, and both iPhone and iPad apps have been fully updated to utilize the new OS. If you are not planning to upgrade to iOS 7 right away, you won't be able to upgrade to Drafts 3.5. But thanks to Apple's newly implemented "last compatible version" feature, you should still be able to download a version of Drafts that works on iOS 6.
Other new features