Proposal for dropping IE 11 support in Vue 3 · Discussion #296 · vuejs/rfcs · GitHub
Though Vue 3.0 is not currently supporting IE 11, there was the idea to ship a compat built that would support it. However, after the recent developments, the team figured that it might be better to instead port as many Vue 3.0 features into Vue 2.x core (including the composition-API) instead. Additionally, the Vue 2.x codebase is being rewritten in TypeScript.