I am an in-stater, heres my story for what its worth
last year int in late Jan, heard 3rd week in march, got a waitlist letter, third tier...
and fyi, third tier = almost no chance of getting in, like 2%.
But i was optimistic, i called to find out my chances, and they said that last year they got through most of the middle tier, and im guessing took one or two people from third tier max if any. Once i told the dean in a phone convo that i was in the third tier and he was immediately like OH, well then, theres not much we can do for you this year...
And i should mention i got NO email titled "application update" last year, just the third tier waitlist snailmail.
This year i got what sounds like the same email as you guys.
I interviewed Dec 1st, heard they would review me again in March on february 6. Just waiting since then.
SO to sum up, i think that if no letter comes soon telling me that I am on the lower third (like it did last year this time with a later int), that means I am either upper or middle, which is a good place to be.
But I do think it is possible that such a letter will come, cuz I think that they just dont break down the waitlist into tiers until around now. So i think the answer lies in the very near future.