If you've been in the Android world as long as I have, then you know by now that there is one thing you don't ask or. And that's an ETA (Estimated time of Arrival). There's one thing you don't want to do and that's rush developers into making a dead line. Then the proper testing doesn't get done and you normally see bugs in the code, which make most people more upset.
JBQ, or Jean-Baptiste Queru took to Google+ to talk about ETA's on OTA's and basically said don't ask about them. As many of us know, Google does not send out the OTA for the Nexus family all at the same time. They need to stagger them throughout a time frame so that their servers don't go down or have any other problems. In fact, it took me about 2 weeks to get the Android 4.2.2 update on my Nexus 7 (for Android 4.3 I just flashed the factory image). JBQ explains the deal with ETA's on OTA's:
OTAs intentionally start very slowly, both in terms of numbers and in terms of timing. The goal is to try to identify catastrophic failures that wouldn't have been found in testing. Those things can happen, unfortunately. From the point where a phase of the OTA is sent out, it takes at least 2 days to collect enough information to make a decision about the next phase.
Phase by phase, the OTA gets exponentially deployed to more and more people, up to a point where enough people are running it to be able to extrapolate even rare issues to the entire population, at which point the flow gets much faster.
The point of going phase by phase is explicitly to be able to stop the process in case something goes wrong, and that's why there can't even be an ETA.
We've said this before, and we'll say it again, don't ask about ETA's. This goes for apps, updates, new ROMs, just about everything that has to do with developers. Everyone understands right?