I've heard from multiple sources that there will be an adapter that will allow Model S owners to charge from a Tesla-plug HPC. I've also heard there might be something eventually to allow Roadster owners to charge from an HPWC 2.0.
The Model S has isolated onboard chargers which means it should not have the ground fault issues that the 2.x Roadsters have.
However, there's a big problem with the orignal Tesla HPCs (not the later Clipper Creek units): if the car is plugged in and the station loses power, when the power comes back on the HPC will go into an error mode and not be able to charge. This means if you lose power, even briefly, your car won't charge again until you unplug and reboot the station. This could be inconvenient on an overnight charge.
Even worse, if you leave your Roadster for an extended period (months) and depend on an original Tesla HPC to keep the battery pack charged, this bug could result in your Roadster being bricked. This is only an issue for the first 200 or so v1.5 (2008 model year) owners.
If you decide to replace your early HPC, please consider donating it for an appropriate public charging location. I already have a couple waiting for appropriate homes and would gladly take another.