A couple of days ago, AOSP was graced with a series of freshly created "l-preview" branches and a massive push of brand new code. As we know now, quite a bit of that code push wasn't truly representative of the L developer preview. (Very sneaky, Google.) Most of the truly new updates belonged to GPL-licensed projects, which Google is obligated to release in a timely fashion. The remaining projects with "l-preview" branches were filled with a recent snapshot from the Master branch.
An unexpected treat came zooming out of Google HQ today as Android 4.4.4 OTAs and factory images have started rolling out for Nexus devices. The updates have already been posted to AOSP and Al Sutton quickly followed up with a list of the changes. Since 4.4.3 is only 2 weeks old, and I/O is merely a week away, we had a feeling this was just a security update, and it looks like that's all it is.