I have a vacation rental in Sonoma that just burned down in the fires, so I'm going through this process myself. With the scope of the devastation the insurance claims process is going to take awhile and all owners will have to go through that before considering selling. That being said, I suspect there will be many homeowners who are underinsured, so they will likely take the insurance money and not have enough to fully rebuild, in which case they would be open to selling.
I have been wrestling with the question of rebuilding and/or buying some of the lots that burned in my neighborhood. The difficulty is in identifying and contacting the owners of these lots - it's not like you can mail them a letter because there's just nothing left.
The other, bigger, question is how long will it take the most impacted areas to recover. The neighborhood that my rental home is located in looks like a lunar landscape. Even under the best case scenario I can't imagine it getting anywhere back to normal in less than 3-5 years. The Sonoma and Napa building departments will be overwhelmed with applications and good luck finding a contractor in the next 3 years.
So if you're thinking about buying some of these burned out lots - as I am - you need to have substantial capital and be willing to wait possibly 5+ years before you'll have something to sell.
Interested to hear other people's takes on the situation.