Canon law is here to help.
From today until August 20th (or probably August 19th, since the action of taking canonical possession typically happens during a Vespers the night before), Archbishop-Elect Aymond will officially be the “diocesan administrator” of Austin (as opposed to “bishop”) and the office of Vicar General ceases. Currently, that role is held by Msgr. Mulvey, but he was stepping down from that position next month as he’s moving on to help with formation at the seminary in Houston.
I’m not certain, but my assumption is Archbishop-Elect’s Aymond’s appointment of Vicars General that were to be effective next month are now void.
The Diocese of Austin will not be officially “vacant” until takes possession of New Orleans.
When that occurs, the College of Consultors, within eight days of the vacancy, elects a Diocesan Administrator until a new bishop can be appointed. If they cannot (for whatever reason) elect someone in that time, then the Metropolitan, in this case, Daniel Cardinal DiNardo, Archbishop of Galveston-Houston names the Diocesan Administrator.
The Diocesan Administrator must be a priest who is 35 years old or older “who is outstanding in doctrine and prudence”.
The Diocesan Administrator has the power of Bishop, except in those matters where the law reserves it to an actual sitting bishop or by their nature (i.e. Sacrament of Holy Orders).
Canon Law is quite clear that this is a stewardship position, that is, one where nothing should be changed or amended that would inhibit the incoming bishop from carrying out his new role. For example, if there is a punishment due to sin (i.e. excommunication) that is within the power of the bishop to life, the Diocesan Administrator can do so. The Diocesan Administrator should not, on the other hand, merge all of the parishes of the diocese into two megaparishes.
Once the new bishop takes possession of the vacant see, the role of the Diocesan Administrator ends.
More later, as always.