CINEMA 4Ds SDK (Software Development Kit) is changing constantly. This has to be done to reflect new functionality and changes under the hood. While we try to keep the SDK as stable as possible, from time to time, we have to introduce bigger changes. Sometimes, even smaller things can cause bigger changes for the 3rd Party Developers. With R12 we switched from single to double precision. This isn't a huge change by itself, just adding some digits to make numerical calculations more precise. But this also meant, that no old Plugin would run anymore and each Developer had to adapt and recompile his plugins. So changes in the SDK are happening all the time, sometimes they are bigger or can have a bigger impact.
We've announced some time ago, that we are working on new foundations for CINEMA 4Ds future. A project, which we have been working before this announcement and which we are constantly working on. As you can imagine, such internal changes will also influence plugin developers. In fact, they already did. The changes developers will have to face (our developers, as well as external developers) will have sometimes more impact, sometimes they won't have that much impact. Thus you can expect Releases with a huge impact for Developers and Releases, with just a minor impact. We will try to balance our development in such a way, that we don't hurt 3rd Party Developers too often and too much, but to proceed, we will need to put an end to old functionalities and introduce new functions and behaviors. So there is a high probability that future releases will have a bigger impact on our SDK, as more and more of the core functionality will get replaced in a way that we can't make a very smooth transition for developers.
I won't give any information about R20 here, so please don't start asking. We will announce news, when it is time to announce them.