Ionic 3 legacy support?

Will there be a support of Ionic 3 for years to come? At least 5 years?

Reason I’m asking is because Ionic 4 will be agnostic of base framework. While that is a great opportunity to use other frameworks such as Vue and React, there are a lot of projects using Angular as the base-framework.

It would be nice that for at least half a decade, Ionic 3 will be supported 100%.