Particle has now released some of the datasheets and reference materials for the new devices.
There is now enough information available to start our investigation whether these boards will work with the existing Carloop or not.
In the second generation devices (Photon, Electron, RedbearDuo), the STM32F10... processor supported CANbus as a microprocessor peripheral. Do the new Nordic processors have the same support? This would not be a show-stopper, but lacking support would greatly increase the magnitude of the project.
[Edit: I just did a quick searh]
I found the product specification for the new microprocessors, and I did not find CANbus mentioned anywhere:
Does the new third generation break out that functionality and make it available on the feather pins? If not, then it might mean designing a 3rd party third generation product, much like how the Duo was developed by RedbearLabs. If the hardware is brought out to the correct pins, then the feather adapter would allow that connection. If it is brought out to different pins, it would mean a custom adapter or maybe it would be simpler to design a CarloopMesh version.
There should be enough information available now to at least partially answer these questions.
On the other hand, the new devices are intended to be part of a MeshNetwork with connection to the Particle Cloud. Depending on your application, you might be better off with a second generation device. Can you elaborate on whether you need mesh capability with Carloop?
Congratulations on getting your order. I placed my order late, so I will be at the end of the initial deliveries. I just hope they are delivered before Christmas holidays so I can have a friend hand-deliver across the border during holiday travel.