The Recreation model still only supports queries through 2017. I don’t have any predictions for you regarding when we might add support for more recent years.
There are lots of papers published from researchers using other data platforms besides Flickr to analyze patterns of recreation/tourism, but they are not using the InVEST model. This paper looks like a review such research: https://www.sciencedirect.com/science/article/pii/S0959378018309920