I have mixed feelings. I think how good or bad it is depends on how well they maintain and police the definition of what an eBike is. If we wind up with folks using what are essentially motor bikes either by just using real eBikes in throttle mode or cheating and passing off things that actually don't meet the stated definition of an eBike then it could be a bad thing.

If it just gets more folks riding who couldn't otherwise, or allows them to be able to haul themselves or themselves and their young kids up the hills, it will be a good thing.

As far as whether there will be hoards of them... In some places yes probably, because there will be rentals available very close by. After all some places there are currently lots of bikes because of bike rental places. Not sure if this new ruling applies to the Virginia Creeper National Trail, but I can imagine hundreds of rental eBikes there if allowed.

It might even get a few cars off the road by having some people ride their eBikes to the parks. I can see that happening frequently in parks in or near metro areas like the C&O towpath, especially the sections closer to Washington DC, Frederick, Hagerstown, and Cumberland.