In general I find this whole "debate" to be a large waste of time.
First, from a practical standpoint, nothing has really changed. In practice in most national parks the "trails" (mostly closed roads, and a tiny number of bike paths) where the rules against e-bikes applied those rules were vigorously not enforced. Enough so that in encounters with Park Rangers on the Going-to-the-Sun Road in Glacier NP and the West Side Road in Mount Rainier National Park the rangers took interest in my e-bike but were absolutely not interested in either ticketing me or even telling me e-bikes were Not Allowed there. As an extreme case in Stehekin, WA they were renting e-bikes last summer and those e-bikes were a fairly common sight on the (closed) Upper Valley Road.
Second, the vast majority of trails in most National Parks and Forests aren't suitable in any imaginable sense for bicycles of any kind. In the very best of cases you should expect to be carrying your bike quite a significant portion of the distance traveled, and in the worst cases there is just no imaginable way you are going to get your bicycle over or around the inevitable obstacles you are going to encounter. On a recent backpacking trip last summer I encountered several large (6' diameter) downed Douglas Firs in a steep ravine; getting around and over them would be best described as a technical climbing problem; there is no way anyone not a masochist was going to get any bike over that!
Third, the problem today is not who has access to what trails. The problem today is that our trails are disappearing at an insane rate. I'd guess that two-thirds of the trails on federal land (mostly USFS land) have disappeared in the last thirty years. In some places that number is more like ninety percent. In Washington State the Backcountry Horsemen and WTA (both good organizations with good people) are trying to help but honestly it is like applying a tiny band-aid to a sucking chest wound.
Fourth, and finally, whatever they are doing on National Park trails, there are literally hundreds of thousands of miles of logging roads, fire roads, and ranch roads that are lightly traveled and make for great cycling. I can easily put together bike trips on those roads where I can ride fifty or sixty miles and not see another vehicle of any kind. If you throw in decommissioned roads that are still ridable there are even more miles and more opportunities for solitude. Probably the very best mountain bike "trails" I know of are on DNR and USFS lands near Darrington, WA. There isn't any official guidebook or maps but there are literally thousands of miles of roads, with views of ice-capped (well, for now) peaks, roaring rivers, and deep spooky forests. So just go there and you probably won't see anybody.
