It doesn't sound like YJIT is being abandoned at all. Reading between the lines, it sounds like they want to invest most of their new development right now into a less-experimental architecture that's closer to other JITs and is easier to develop, but that they consider this a somewhat risky endeavor and aren't sure whether this investment is going to pan out in the long run. So they're going to try ZJIT out, but YJIT and the ideas behind it are by no means abandoned. They're just taking a pause to see if a rewrite will make it easier to maintain or produce better results in the long term.