Maybe, but it seems Tesla is a bit protective of their tech. Would they void warranties if a problem arose from an unauthorized 3rd party accessory? I wouldn't put it past them.
They already told one of my friends that they would void his warranty if he attempted to make a CCS adapter for his Model S. To be fair to Tesla, though, the Model S requires a Power Line Communication module to be installed into the harness and tied to the BMS. It's a fairly involved process.
The Model 3 (and presumably the Model Y) appear to be natively compatible, so it might be as simple as wiring a physical adapter.
Either way, the door was opened with CCS2 in EU. Eventually, pressure will mount for Tesla to open SC sites to "compatible" CCS2 vehicles. If, for no other reason, it could become a politically popular topic that politicians seek to exploit (not very jaded am I?).
The same could eventually happen here in CCS1-land. The thing that would make this more likely is growth of the CCS community reaching or exceeding Tesla. At that point, the value of the SC network would be far less strategically than current.
I really don't think regulators will get involved here. Europe is a lot more hands on.
At this point, though, you're right. It's not a question of if the CCS infrastructure in the United States will exceed the Supercharger Network, but when. Electrify America alone at this point (with over 2,000 active chargers) represents a quarter to a third as many plugs as the entire U.S. Supercharger Network, and this partnership between GM and EVgo represents a larger percentage even than that (2,700 chargers). And that is on top of EVgo's current count (~1,600 chargers). It's also not counting ChargePoint (I don't have an exact charger count for them, but it should be 1,000 to 1,200), EV Connect, GreenLots (now under Shell Recharge), and a number of other municipal and regional networks.
Also, thanks to Electrify America and this partnership with EVgo and GM, the public charging infrastructure can no longer be poo-pooed as some slower, less capable standard. People are still attempting to dismiss these efforts, of course. "Oh, but these aren't dedicated travel chargers!" "Oh, but they
only have four to ten stalls per site!" "Oh, they're just compliance networks!" But at least the naysayers can't still say that these chargers aren't as capable of recharging a vehicle just as quickly.
And at that point, you're right. The Supercharger Network will have less strategic value than it does currently. Don't get me wrong; it will still be a selling point. We still see this today, where Tesla owners proudly proclaim, "Well, we can use all those chargers too!" Some aren't even aware until I inform them, however, that they can only use the CHAdeMO plugs, and even then, only at a reduced rate. So they can't really "use all those other chargers too." I'm actually hearing more and more frequent gripes from Tesla owners that Tesla hasn't released a CCS adapter yet. It seems like a bit of FOMO, but I'm happy to hear it nonetheless. The sooner we get Tesla owners using the public CCS charging infrastructure, the better.
I give a lot of credit to Tesla for having the foresight to plan and deploy the SC network to support Tesla owners at times when few were getting into the game. They clearly paved the way for adoption of their cars. But, competition is catching up. It might even reach a point where the SC network is a liability to Tesla if it goes underutilized due to the capacity or convenience of the CCS networks. At that point, they would be eager to open up SC sites to other EVs.
From a technical point, the plug compatibility is one challenge. But, the billing part is probably bigger. 3rd party EVs would need to support Plug & Charge, or else payment terminals would need to be added. Neither in insurmountable, but both are deterrents to open, universal charging networks.
Yes, Tesla deserves a lot of credit for building out their network, but they also deserve credit for maintaining it as a walled garden. Initially, I believed the hype, too. Tesla was a pro-EV company, and they wanted all EVs to succeed! However, when asked repeatedly to provide a Supercharger adapter (Tesla could have even profited off it!) to support all EV owners, they refused. Time and time again, they deflected to the other automakers not wanting to chip in or support the Supercharger Network. It wasn't about those automakers, though. It was about the EV community. In my opinion, Tesla failed that basic test of whether they actually supported the EV community as a whole.
The plug-and-charge functionality and integrated billing are crucial, you're absolutely right. Both of those, though, are being worked on. EVgo is working on a plug-and-charge functionality that should even be backward compatible with EVs such as the Bolt EV. Automakers such as Ford and Mercedes are also introducing a single billing portal, out of which all your charging (regardless of network) is paid. At this point, we're looking at less than five years before almost every new EV sold has the same ease of use that Tesla owners currently enjoy (plug-and-charge, integrated billing, integrated route planning, etc.).