If we consider where the LPC came from in 2011 a CPC win in 2019 is not impossible. However, the party might need to realize that it could be in opposition for an extended time. I think they need to consider a leader that is effective in making sure the Liberals don't veer too far to the right.
An example would be the 90's which I feel despite the issues in the conservative movement the liberals cut deficits, cut taxes, etc. The present conservative movement might need to play more defense than offense.