Elizabeth Scalia has the scoop on the decree just issued:
The decree was prepared and signed by Cardinal Robert Sarah of Guinea, prefect of the Vatican’s Congregation for Divine Worship and the Discipline of the Sacraments, and released with an accompanying letter from His Holiness, in which the pope writes that he has long-reflected on the “rite of the washing of the feet contained in the Liturgy of the Mass in Coena Domini, with the intention of improving the way in which it is performed so that it might express more fully the meaning of Jesus’ gesture in the Cenacle, His giving of Himself unto the end for the salvation of the world, His limitless charity”. “After careful consideration, I have decided to make a change to the Roman Missal. I therefore decree that the section according to which those persons chosen for the Washing of the feet must be men or boys, so that from now on the Pastors of the Church may choose the participants in the rite from among all the members of the People of God. I also recommend that an adequate explanation of the rite itself be provided to those who are chosen”. The order has gone out, and instructions in the Roman Missal for Holy Thursday will be changed immediately, and applicable to this year’s ceremonies, on March 24.
There’s more, including the full text of the decree, at the link.
The salient paragraph:
To manifest the full meaning of the rite to those who participate in it, the Holy Father Francis has seen fit to change the rule by in the Roman Missal (p.300, No. 11) according to which the chosen men are accompanied by the ministers, which must therefore be modified as follows: ‘Those chosen from among the People of God are accompanied by the ministers’ (and consequently in the Caeremoniale Episcoporum No. 301 and No. 299 b referring to the seats for the chosen men, so that pastors may choose a group of faithful representing the variety and unity of every part of the People of God. This group may consist of men and women, and ideally of the young and the old, healthy and sick, clerics, consecrated persons and laypeople.