Ionic Framework is still fully based on Angular, it will just be using Custom Components (bundled in a package called @ionic/core) inside instead of the "Angular built Components" (no idea how to name these...) in v2+3. These custom components are built using the Stencil compiler by the Ionic team, but as a Ionic Framework user you won't (have to) come into contact with that at all.
These new components can be used in other frameworks like React etc as well - or even AngularJS (Ionic v1!) or plain Javascript.
Here is a currently working link to a branch where this is developed (pre-alpha, so can change of course): https://github.com/ionic-team/ionic/tree/core/packages/ionic... & https://github.com/ionic-team/ionic/blob/core/packages/ionic... As I see it mostly the syntax and attributes of components were cleaned up.
Ionic Framework is still fully based on Angular, it will just be using Custom Components (bundled in a package called @ionic/core) inside instead of the "Angular built Components" (no idea how to name these...) in v2+3. These custom components are built using the Stencil compiler by the Ionic team, but as a Ionic Framework user you won't (have to) come into contact with that at all.
These new components can be used in other frameworks like React etc as well - or even AngularJS (Ionic v1!) or plain Javascript.
An alpha of v4 is planned pretty soon I hear.