I just didn't think Pypy belonged in the same category as Pyston. There have been a few similar projects - Pyjion, Unladen Swallow and Nuitka also come to mind - each of them are/were impressive pieces of engineering, worthy of our admiration. But each of them have also seemed to hit a wall of some kind and have fallen by the wayside, as you said Pyston has. Meanwhile Pypy has stuck around for fifteen years, it may not be CPython but it'll still be around for a while yet I imagine.