Start with V3 or proceed with V4

Hello everyone, 

Since about 5 years CI is my prime weapon of choice when it's comes to developing web applications. I've always liked the fact that you can use CI without getting in the way like a lot of frameworks do. Anyway.  At this moment I'm about to start a few new projects. They will hit development just in a few weeks, and we focus on production within a few month's to about an year or so. 

Anyway, at this point I need to make an decision. Will I use V3 for this new projects, or shall I already move to V4, assuming that in a certain point both development path's meet. 

Any input is highly appreciated!