The kinds of things Specter mentions are already happening. You can’t ride an Onyx RCR anymore in a lot of California cities without getting pulled over, for instance. You might still get away with something equivalent that looks more “bicycle.”
I see high-powered e-bikes as a new take on old 49cc mopeds. No insurance and lax registration requirements, but you wouldn’t want to ride one on a main road unless it’s in the bike lane. Here in Sacramento, I can get around the slower streets of our neighborhood and downtown on a bicycle, moped / e-bike, or 125cc scooter / motorcycle equally well, but as soon as I go past any freeway underpasses in any direction, the 125cc is the only one that can still hang with traffic and not make me feel like I’m going to get run over.
Just like mopeds, e-bikes can technically be built or modded to hit 45+ MPH, but they’re still not safe to ride on a 45 MPH road. E-bikes aren’t safe because drivers will assume you’re going to be a slow obstacle and drive insanely aggressively to get around you*, mopeds aren’t safe because they may have the top speed but they don’t have the acceleration and also invite aggressive driving, and both aren’t safe because they don’t have the suspension, brakes, and tires to handle potholes and other conditions at those speeds, especially non-DOT e-bikes.
I do like e-bikes and see the potential, but when I got our 150cc Chinese Lambretta clone, it hit me that all the things e-bikes can do, scooters have been doing cheaper and better for decades. Acceleration, top speed, safety, storage and utility, all vastly better than an e-bike. Usually more sustainable because small-displacement scooters get 90+ MPG and don’t get ridden a huge number of miles, which makes their lifetime carbon footprint really small, probably smaller than something whose battery had to get manufactured using materials from all over the world and shipped ten thousand miles. Assuming I change the oil and adjust the valves, my Znen scooter will run just as well in 10 years as it does now, can the same be said for an AliExpress e-bike? The only real advantage in California is you don’t have to insure an e-bike and pay the usurious annual registration fee, but I don’t expect that to last forever, either. I’m not against e-bikes and have built and owned several, I just don’t think any e-bike is a serious replacement for a scooter or motorcycle over 50cc.
*I once had a guy pass me doing over double the speed limit around a blind corner in the incoming traffic lane, he’s lucky he’s still alive. Actually that was 10+ years ago so there’s a good chance he’s not, driving like that.