Comparing Python release dates to the first MATLAB releases that support them, it appears MathWorks consistently takes about a year to add support for a new Python version. So my hopes are high for R2020b.
Python 3.4.0 released 03/17/14, supported by R2015a (I can't check documentation for R2014b)
Python 3.5.0 released 09/13/15, first supported R2016b
Python 3.6.0 released 12/26/16, first supported R2017b
Python 3.7.0 released 06/27/18, first supported R2019a