When they updated CI 3.x ?

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Hello support team, I'm worried about only seeing updates of the CI 4.x version and I wonder:
- Why the CI 3.x version does not have updates?
- Will you stop supporting it or giving it support?
- When we wait for a new update?
- What is the time lapse between version and version?

by last:
- If you intend to do disappears CI 3.x will you give the community a tool to migrate from 3.x to 4.x? or will it be something personal and manual?

Important: what maturity do we expect from the CI 4.x version to involve it in our projects? and meanwhile we have done with CI 3.x
thanks for answering
*non-English redacted*