From every bit of information that has come our way it seems as though this has been the best season for Grifola in decades. As several collectors have commented, “They are everywhere”. An exaggeration to be sure, but it does point up the relative abundance of this (and other) mushrooms this year. One Mycologist suggested that this may be the best year in a century, and will be remembered as such!
As to your question: Since Grifola (like most di- and tri-mitic Polypores) takes such a long time to develop within the substrate of their hosts I don’t think that you can count on spores from this year to produce much in the immediate future. (See the response to Zoe’s question below.) But if you are thinking of your children – or perhaps grandchildren, well… hope does spring eternal.
Pushing your question just a bit further: To my mind the best thing about mushrooming, better even than consuming a flavorful meal, is the quiet focused search. During melancholy walks in the fall woods I might try to convince myself that I am looking for mushrooms, but if truth be told, I am really searching for parts of myself which have become dislodged by the more hectic activities of a modern life style. To this end the surprise and jolt of energy when I find a new tree (or species) is the thrill which fills my sails and carries me onward. For me, the new find is much more valuable than returning to a known, proven place.
As a boy on our farm in Western Pennsylvania I often became lost in the hills and forests which surrounded the fenced-in gardens and pastures. It was in those moments, hours, that I came to understand about intuition, self reliance, and what is often referred to as the Godhead Within. I suspect that looking for mushrooms today, and becoming lost in that pursuit, is an expression of that early experience. It is an extension of the known into the unknown.
In this sense it seems as though (for me) hunting for mushrooms is expansive whereas cultivation or gardening is grounding. Both obviously have their place, time and function.
Zounds! I didn’t know your simple question would take me here, but here it is! Thanks for asking.

Welcome to the blog and thanks for your comment. Your question reminds me of the old saw about the fellow who looked for his lost keys around the lamp-post because the light was better there. I guess frondosus may be easier to spot in open areas compared to the woods, but almost all of the fruitings I have found in 40+ years of collecting them were on trees in the woods. The few not in the deep woods were usually on large old oaks at the forest/pasture edge. Given your observation, it may be that someone else was able to beat me to the ones visible in the yards.

I have found Hens on Maple only three times, all in separate years at the base of the same Maple – which was at the edge of a yard.

But, as they say about finding Morels; they are where you find them.

I am not familiar with the precise mechanism by which G. frondosus becomes a pathogen of oaks. There are a web pages with a wide range of views which appear when a Google search of “Grifola root damage”. One from Europe postulates that within the extensive life span of a 300 year old Oak tree the same species of fungus (Grifola) can operate as a symbiont partner. a weak parasite, and a severe pathogen at different times in the lengthy evolving relationship of the two species. In this scenario, the ‘infection’ is likely to have begun prior to the invention of the internal combustion engine, let alone lawn mower. http://arbtalk.co.uk/forum/fungi-pictures/33528-grifola-frondosa-assessment-thermo-twist-2.html

By contrast, in a quite straightforward paper from North Carolina, the lawn-mower hypothesis is cited as a cause of damage which allows fungal spores to penetrate and take up residence within the Oak Tree. http://www.ces.ncsu.edu/depts/pp/notes/Ornamental/odin30/od30.htm

Both of these papers seem to deal with the type of habitat you describe, parks and urban landscapes.

You are lucky to have begun your quest for Grifola in a very good year. Indeed, here in the Hudson Valley, and along the coastal plain in Connecticut they seem to have been particularly abundant this year (although interestingly they did not reappear on the Maple where I have previously collected them.)