According to Maximilian Hanlon, and other sources, the replacement for Cardinal Mahony should be the Opus Dei Archbishop from San Antonio, His Lordship, Jose Gomez.
Bishop Gomez was sent to the San Antonio See in 2004 and had been shepherding the Archdiocese of Denver as Auxiliary Bishop prior to that.
He was a lot more generous with the Immemorial Mass than Cardinal Mahony was and had this to say about the Motu Propio:
... pope's move will help Catholics "be able to clearly see the growth and progress we have realized since Vatican II, while at the same time preserving the rich heritage and legacy of the church." 
If he promises to be like his fellow Opus Dei Bishop, Archbishop Finn of Kansas City, this should be a real welcome to the auto-destructive regime of one of the most scandal ridden clerics in the history of the American Church. Archbishop Finn once reminded Catholics that we are in the Church militant and "in a war". Such triumphalist language shows well on Opus Dei.
We would also like to say that this posting is typical of the appointments by Pope Benedict. Earlier this year, he appointed the most conservative Bishop in Belgium to lead the country in Brussels, Archbishop Andre Joseph Leonard . Or the new Auxiliary Bishop of Linz, Father Wagner, who was shouted down by the liberals in that most challenging Austrian Diocese. Or Bishop Jose Munila of Spain in December.
Another not so surprising appointment was Archbishop Carlson, formerly of Sioux Falls and Saginaw, who had a legendary reputation for administration and conservatism.