I know I am not WN's target market, but California to Hawaii is too long a flight for me to buy without a confirmed seat assignment. Also, having E+ is very important to me on a flight that long.

Though, I recall reading that the 737-MAX will have more generous seat widths.

But bocastephen is right: it depends on the exact routes. I feel like LAX/SFO are fairly saturated to Hawaii already. And although it is a leisure destination, it is generally (though not necessarily) a more expensive one than, say, Florida, so I don't know how much more demand there will be just because the flights are cheaper.