Since the new devices are not yet released, there is no way to be absolutely sure.
In terms of hardware interface, we do know there will be differences, since Particle has created an adapter; see this link:
In terms of the system firmware, and support for CAN, we can only assume it will still be supported. However, it is still an assumption for all its worth.
Also, in the particle community, I recall a post where Particle committed to continuing to support the existing hardware, meaning we can expect to still be able to get Photon and Electron devices.