Mason's naysaying is more related to his growing concern for Notley than about anything getting "ugly" 
Here's what is most likely to happen:
* Kenney will win the PC leadership and move to create a third united entity.
* Brian Jean and Kenney (and others) will compete to lead it (Conservative Party of Alberta(?))
* The Redford faction of the PC's (e.g. Sandra Jansen) will noisily leave for their natural home in the NDP.
*  Anyone for whom the new entity is not "right enough" will grumble, think about the alternatives, and either join up or not vote.
* The provincial Liberals will replace their excruciatingly pedantic leader with someone more media friendly and start to bleed votes off the NDP.
*  The CPA will win a majority in 2019.  Liberals will win opposition. The NDP will be steamrolled into third or fourth place.
y'er welcome, Bart