As of today, there are 226 living Cardinals. Of those, 120 have the right to vote in a Conclave when one becomes necessary (aka, they have not yet turned 80 years old). These are called the Cardinal Electors.
The limit of the number of Cardinal Electors is 120, although the Pope can ignore that if he so desires.
This year (2017) only four Cardinal Electors turn 80. That makes a consistory to create new cardinals this year unlikely.
Next year (2018) is a different story - seven additional Cardinals turn 80. In an odd streak of luck, all of them fall in the first half of the year.
Assuming no deaths, that means that 11 Cardinal Elector "slots" will be available by June, 2018. So I'm predicting a Consistory to Create New Cardinals in late Spring or early Summer 2018.
With the effort of Pope Francis to de-emphasize the Roman aspect of the pallium distribution, perhaps the weekend after the Solemnity of Sts. Peter and Paul would be a good time.
In 2019, an additional 11 Cardinal Electors turn 80. Four of those fall in October. Thus I'm predicting another Consistory to Create New Cardinals in late Fall 2019.
The weekend of Christ the King (23-24 Nov) would be an obvious choice but there are other options such as All Saints/All Souls or the Dedication of the Lateran Basilica.
(Note I had previously predicted a consistory in the "Spring of 2018" in this post back in November 2015.)
Of course, I have no inside knowledge and the creation of cardinals is at the complete discretion of the Holy Father.
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