In case it wasn't clear, mine above was a conjecture.
You are correct that there are not many examples, but there ARE some, like the end of Rogue One with Princess Leia.
Soon is a very relativistic term when it comes to technology advancement. I myself have played around with TensorFlow and swapped my own face for that of Neo in the Matrix. Trivial stuff actually. I get my AI info from my practice as a software developer. I am only inferring of what will become possible to do in the near future when more potent computation becomes cheaper and available as well as better training models for machine learning.
This WILL be possible. And what's more: I suspect it will not need big studio funding to get it done. It may be a fan driven effort. Not just with this show, but with any other. Future TV/Cinema productions will be cheaper by orders of magnitude with the advancement of this technology. It's only a matter of time. True, 2025 was an arbitrary date, only meant to get attention: but certainly this decade.