My thoughts on this bloc of undecided voters is thus.
They will not stay home.
If they do, my projection is going to be way off, because if they do, the PQ wins a majority. I think, however, that there are enough people genuinely scared of a PQ government that they will be motivated, at minimum, to get off their bum and cast a ballot. The "problem" here is that some undecided voters may be PQ-QS-ON, and thus, this elimination may not work.
They will not split their vote.
I can't see such a large and consistent bloc of undecided voters deciding to split their vote between the parties. Normally, when undecided numbers fluctuate, it is more likely to see a split, but my experience has told me that a more consistent number, like that we've seen in this election, is more likely to have their votes swing towards one party much more than to another.
So will they go PLQ or CAQ?
I don't know. That is the last question that remains to be answered. That, as well as, how much of a swing to the party will there be? Too small, and the PQ wins.