Well should there be a minority (seems unlikely given what the Liberals will be reduced to), the greatly reduced OLP (with what - like 5 seats?), Mike Schreiner of the Greens and the NDP should surely agree to move towards proportional representation in Ontario.
I doubt they would get the libs to agree to that - they benifit from FPTP. Same reason Trudeau quietly dropped the issue after he won.
If this is such a big deal then NDP and Greens should work out an alliance model where they have seat adjustment since there is no way LIB or CON will agree to PR.