Grapp -- I think he'll wrap Winds of Winter pretty soon. I think A Dream of Spring may not make it. He admitted to not having even starting that one, which is, unsurprising, but still ridiculous. My guess is, he'll outline it once WoW is done, and from there, we cross our fingers and hope he does eventually get it done. He had so much success late in life, he's trying to capitalize and take advantage of everything brought to him. I can't blame him, honestly. But I know if it were me, I'd want to wrap it up quickly, so I could go on and enjoy all those other opportunities, without the prospect of writing looming over my head.
As for other stories, I am undecided. I have Fire & Blood and haven't started it yet. It's on my list. But generally, I'm not big on prequels. I would actually like to continue following Arya, Jon, and even Tyrion from his perspective. It seems those characters could continue to make compelling TV on their own, as the primary characters.
And for those that mentioned Chernobyl -- watch it. The third episode aired on Monday, but I haven't watched it yet. The Mrs. and I watch them on Friday nights, so we've only watched the first two. Compelling, dark, haunting. Totally worth the watch.