While I haven't played with Lumen and don't like Laravel all that much, I'd like to see CI4 become a micro-framework, where anything except the core is a component or package that is easily pulled in or installed via download. I've used Slim quite a bit and at one point had transformed most of the CI classes for use with it. When I finally realized that all I was using Slim for was routing, I created my own framework using Pimple, made my own router, and moved away from Slim.
I think the direction that I went, while "modern", is probably a little more advanced than many CI users would like. If we were to go in this micro-framework direction, it would be difficult to be that "easy" framework that everyone loves. I care about that, because I keep coming back to CodeIgniter just because I can get stuff done super quickly. I'm not just playing around. I have businesses and make websites professionally for people, so working quickly in a super easy environment is essential to what I do.
With all that in mind, I'm hoping that we can have a CI4 that is super easy to use, yet embraces some of the workflow that many other frameworks are utilizing. Can we have a micro-framework without blowing away the newbs?