Now more information has surfaced regarding iOS 7.1.2, and it looks like the update will bring fixes for mail, Lock Screen and iBeacon issues. According to sources, 7.1.2 does indeed fix the email attachment encryption issue as well as another bug impacting email downloads. There will also be a fix for a lock screen bug that can allow users access to limited apps in certain circumstances. Finally, 7.1.2 will be bringing improvements to iBeacon connectivity and a bug fix that addresses data transfer with third-party accessories.
The sources did not mention anything about the iMessage bug that impacts users when switching devices, but it is likely that Apple quietly included that fix in the build.
Apple has begun seeding iOS 7.1.2 build 11D257 to carrier partners and has requested them to sign off on the update by Friday, June 27, which hints towards a public release following that date. iOS 7.1.2 will likely be the last iOS 7 release until iOS 8 lands this fall.