Unlike desktop environments where there were equivalent alternatives to Unity, Flatpak isn’t an alternative to Snap that can deliver an equivalent solution. You can’t build an OS on top of Flatpak. This is why I think that if Snap makes the lives of Canonical developers easier, they’ll keep maintaining it. We’ll know if Ubuntu Core Desktop becomes a mainstream flavor or the default one. I think there is a commercial value of it in the enterprise world where tight control of the OS and upgrade robustness are needed. In this kind of a future Snap will have a long and productive life. If it ends up being used only for desktop apps which Flatpak covers, it may fall by the wayside as you suggested.