The best answer can be given by Cardboss itself...
However, I know that if there is a serious bug or so in the software, it will be repaired. That is happened a few times after the shut down moment. However, there are always bugs in software, but I think it will hard to find them in Cardbox...!
Also in the newest Windows versions, it runs ok. So the software does not need patches to run in W10 of W Server 2018 or so...
It is a pity for me and perhaps others that none of my almost 100 wish-items not one will be implemented any more.
Cardbox deserves more success. However, we have to face that the actual success is not not big enough to implement new features or to develop a fresh interface. That would cost many many hours. And it is not real to expect that these hours can be paid by the (too) small Cardbox community.
So, consequences: I think there a little: official support it is there not any more. However, there are a few Cardbox experts that can support people as they need it (and build applications). I am one of them. Also I think a little to establish a foundation for "saving Cardbox knowledge". But this is only a thought on this moment.
Personally I see no big problem by the knowledge Cardbox is not supported any more. It works, as it always did and the current versions are very stable. I hope this gives you a little confidence.
It's disappointing that there will be no further development and no fresh interface in the future.
I've asked Martin before about us paying for additional feature development and also the possibility of releasing the source code so that other developers can continue with it but the answer was no.
I would have hoped that there would be other options other than ceasing such as making it open source, selling on, crowdfunding, etc. but understand that's for Cardbox to decide and I'm sure they have reasons!