At this point over 3 million acres [1] have burned in CA alone. So, seems like some of the 20 million acre backlog is getting burned through this year.
OK, so in three equivalent years, 50% of what needs to go will be gone - and that will give "herd immunity" to the unburned parts - 'till those get large again, say in 5 more years.
1: https://www.fire.ca.gov/daily-wildfire-report/