In Jetpack's favor, it has a powerful module system similar to the one in node.js. However, given that JavaScript will soon have built-in support for modules, this won't be an advantage for long.
Finally, Jetpack doesn't solve the problem that add-on developers must code maintain a different codebase for two very different APIseach browser. Basing WebExtensions off Chrome's API means that developers who stick to the common APIs will only have to maintain one codebase.
=== Which add-ons will stop working after the deprecation? ===