Is Codeigniter 3 php 7 ready?

When CI3 was released, PHP7 wasn't even in Alpha stage (IIRC), so you can't reasonably expect it to be ready for that.

That being said, it is being tested against nightly PHP7 builds and it should run just fine on it, there's no reason not to. If something breaks under PHP7, we'll fix it, if that's your question.