Announcing Citi and selling tickets tomorrow makes every logical sense.
Assume, as I do, that the club wants to start selling no later than Oct 18, which has always meant a decision by October 17 (potentially overnight). The original schedule allowed for 2 possibilities: the Astros win by the 17th, and we play at YS, or the Astros don't win by the 17th, and we play at Citi. We could have found out earlier had the Yankees won 2 early games but they did not.
Now there is only 1 result possible: the Astros will not win the series by the 17th. It just cannot happen any more. That means Citi Field. There is no need to delay. They might not announce today but I bet the STH presale starts tomorrow no matter what.