Yale is usually one of the later ones in sending admissions letters - last weeks in March to first weeks in April is normal.

The average architecture school Dean lasts about 6 years, so changes in leadership are a regular occurrence at most universities.  It may or may not eventually affect admissions procedures.  It does tend to have have some impact on the pedagogical and stylistic preferences of admissions committees, as the makeup of the committees is of course impacted by changes in faculty appointments, over which the Dean typically has influence.  These shifts, and any major ups and downs in financial aid availability, typically take at least a year or two into a new Dean's tenure to manifest in any noticeable way. 

What I would like to see Yale change is the draft of its admission letter, which for more than 25 years has include the line "while Yale always receives many well qualified applicants, this year's accepted class is particularly strong".