With most versions of Android, we're not used to seeing a changelog until a few hours after the AOSP code has been fully uploaded and somebody has had time to generate a comprehensive list. Imagine our surprise when such a list for KitKat 4.4.3 was discovered simply lying around on Google's servers. The file, named KK-MR2_changelist.txt, is located amidst Android's platform documentation. This is something of a first, since we'll actually learn about what's to come before the code is even available.
The changelog was first added 3 weeks ago, but it may not have been uploaded to AOSP until more recently. Judging by the build numbers listed and the relative position of the 4.4.3 tag, there's a good chance KTU70 is going to be the final release. That particular version would have been built on March 11th (build number parser).
This changelog seems to contain every accepted modification since KitKat 4.4, not just those from 4.4.2 - and at 5293 lines of text, it's certainly not a quick read. We'll be working on cutting it down to just the new submissions, but in the meantime, everybody is welcome to do their own looking around. Developers often leave clever or witty remarks, so be on the lookout for a couple of good laughs.
7503e73 4.4.3 is MR2, version boogaloo!
It's fairly common for Google to ship one final update to the Nexus family in the weeks leading up to a major release, which we can probably expect for I/O 2014. In other words, don't be too surprised if a flood of updates begins rolling out really soon.
Update: Google has taken down the changelog, but there is a copy mirrored on Github.