The problem with that statement is what exactly does "in a way that maintains GPL compatibility" means, especially since they plan on moving more functionalities into the proprietary code, so the two "separate" components will be increasingly coupled together.

I'm not a lawyer, but I'm quite skeptical of the outcome. Is it really going to produce a valid GPLv3 licensed client? To me, it seems like the whole thing is just going to be a combined proprietary + GPLv3 license, which will contradict itself.

But again, I'm not a lawyer, so my understanding of this might be way off.