Yes, I’m skeptical that WT will incorporate his design, as it is a big design change. There’s no way to just “plug it in” somewhere, without replacing the beating heart of WT. It would be great if they did that though, and I’d applaud them for it.
I think Casey did a lot of other great work on more correct and speedy non-ASCII support, and very efficient scrollback (in both memory and time cost), etc. It's been a while, but I think the atlas approach is also different. But kudos for what seems to be a good step. I'm curious to see some data on the resulting performance and memory usage (presuming the latter is mostly unchanged).