One constant will likely be that time is of the essence. The sooner you notify the park (giving them time to attempt to secure another renter) the more likely it will be that they will make accommodations. It is also possible you might lose some priority benefits such as getting a personal favorite site each year. Renters who do travel this year will want the best sites and your site would now be available for them to choose. They may very well have first dibs on that site in subsequent years.
I could also see parks having different policies based on where you are coming from. Since Canadians cannot cross the border with their RVs at this time the park may offer special consideration for them over someone from Michigan who just doesn't want to travel. The Canadians in this scenario have no choice, the Michigan resident is making a choice which is a big difference. To me, the Michigan resident choosing not to travel because of COVID is not much different than them choosing not to travel because the long range forecast is for a rainy winter in Florida or because the price of gas has risen 50 cents. Personally, I would have a very liberal policy on deposits for the Canadians and adhere to my standard refund policies for US residents.