Migration 2.2.x to 3.1.4 OR waiting 4.x

Hi 

I am building 2 apps that are used by company and they were all based on 2.2.x.  I am still on the process of 
migrating to 3.1.4.  However my question is that if it is worthy to migrate to 3.1.4 and if it is then how long
3.1.4 will come to end of support ?

My concern is that CI 4.0 will change a lot versus Ci 3.x as far as I know.

Please advise!

Many thanks