It is generally assumed that Pope Francis (and it isn't Pope Francis I) will soon appoint a new Cardinal Secretary of State. IF His Holiness follows the example of his predecessors, and it cannot be assumed he will, then the appointee will already be a Cardinal.
Checking back as far as to the appointment of Fabio Chigi in 1651, only four prelates were not already Cardinals upon appointment as Secretary of the Secretariat of State. From the appointment of Fabrizio Cardinal Paolucci for a second time (in 1724 under Pope Benedict XIII; he had served as Secretary of State under Pope Clement XI from December 3, 1700 until March 19, 1721) the general rule has been that the Cardinal Secretary of State has been a Cardinal upon appointment. Cardinal Paolucci himself died prematurely and had to be replaced, and his replacement was not already a Cardinal (see below).
It should also be noted that two prelates were on the same day created Cardinal AND named Secretary of State: Ercole Consalvi (August 11, 1800; first appointment) and Luigi Jacobini (December 16, 1880). Note, also, that Domenico Cardinal Ferrata was named Cardinal Secretary of State by Pope Benedict XV on September 4, 1914, but he died soon after, on October 10, of peritonitis after an illness which lasted several weeks (because of which it was considered imprudent to operate). He was replaced by Pietro Cardinal Gasparri.
The four non-Cardinals upon appointment as Secretary of the Secretariat of State were:
(1) Fabio Chigi, Bishop of Nardò, Italy, was Apostolic Nuncio in Cologne June 11, 1639 until 1651. Pope Innocent X (1644-55) appointed him Secretary of State in early 1651 (exact date unknown). He was created Cardinal Priest in the title of Santa Maria del Popolo at Innocent X's Consistory VI on February 19, 1652. He was sent as envoy extraordinary to the conference of Münster, 1644, which culminated with the Peace of Westphalia, 1648, ending the Thirty Years’ War.
Cardinal Secretary of State Chigi was elected Pope Alexander VII on April 7, 1655. He died on May 22, 1667.
(At that same consistory of 1652, Pietro Vito Ottoboni, auditor of the Sacred Roman Rota, was created Cardinal Priest in the title of S. Salvatore in Lauro. Elected Pope Alexander VIII on October 6, 1689 (died February 1, 1691)).
(2) Giulio Rospigliosi, Titular Archbishop of Tarsus, formerly Apostolic Nuncio to Spain, was living in retirement (1653-55) when he was named Governor of Rome by the Sacred College of Cardinals during the sede vacante, January 8 until April 15, 1655. He was appointed Secretary of State by Alexander VII (1655-1667) at some point in that April of 1655 following upon Alexander VII’s election and served until May 22, 1667. He was elected pope on June 20, 1667, and took the name Clement IX.
(3) Federico Borromeo Jr, Titular Patriarch of Alexandria, Apostolic Nuncio to Spain, was named Secretary of State in May, 1670, following upon the election of Clement X on April 29. On December 22, 1670, he was created Cardinal Priest in the title of S. Agostino. He opted for the title of S. Agnese fuori le mura, August 8, 1672.
(4) Nicolò Maria Lercari, Titular Archbishop of Nazianzus, was appointed Secretary of State on June 14, 1726, by Pope Benedict XIII (1724-1730) following the death of Fabrizio Cardinal Paolucci. He was created Cardinal Priest in the title of Ss. Giovanni e Paolo on December 9, 1726. He served as Benedict XIII’s Prime minister and Secretary of State until February 21, 1730.