According to Morrill, the first 24-48 hours of a rollout are typically reserved for 1% of devices and Google will wait to see if there are any reports, which if there are, the update will presumably be halted temporarily until Google fixes it. However assuming nothing goes wrong, what happens next is that the update will then be pushed to 25% of devices, 50%, and finally 100% over the course of one or two weeks. This is a surprisingly long process but like we said, now that you know, don’t worry if your friends got the update ahead of you because it will arrive for your device eventually.
Interestingly enough according to Morrill, it seems that this is done on random, and that when your device “checks in”, there is a chance of it being offered the update, but assuming it doesn’t get the offer, you will then have to wait for the next batch. For example if you missed out on being in the 25% batch, you’d have to wait for the 50% batch, and etc. Pretty interesting stuff, isn’t it?