Yes, that would only be for a 50A circuit on a wall connector. Given an all electric house, you probably have large loads (heating and water heating) that eat up a lot to most of your load calc, leaving not much left to charge a car.
The good news for you is that if you only have 50A of headroom total, a master/slave wall connector would allow you to actually charge two cars at once, either one utilizing the full amount when possible. The alternative would be to manually ensure they never charge at the same time (yikes, that would be hard to ensure you don't screw up), or have two smaller charging circuits like a 6-20, and neither car would be able to charge at even reasonable speeds.
Also, I hope I didn't give the impression that it's cheap/easy to uninstall a wall connector and take it to your next home. My situation is fairly unique that I'm not an electrician myself, but grew up in a family of electricians so I'm familiar with things, and comfortable doing work myself with supervision from brothers/dad that are licensed electricians. Actually paying an electrician to uninstall a wall connector and blank it off/convert to a 14-50 would probably be a good portion of the cost of just buying a new one.