First of all Godot 4 is not "around the corner" by any reasonable estimate. We might have the first alpha this summer, but the alpha -> beta -> release process is going to take some time. There is so much new in 4.0 that it's going to require a lot of testing before it can be anywhere near considered "stable".
Features are going to break, change, and could cause any project made with an alpha to need to be completely restarted. The only reason to be using 4.0 right now is if you are a developer working on 4.0, or you're looking to help with testing. Any work you do on a project using 4.0 should be considered disposable.
In your 8-12 month development time, you may see a release of 4.0, but even then it's unlikely you'd want to use that for your project just yet. Unless you plan to write your own mobile ads plugin, you'll need to wait for those to become stable and tested as well.
Short answer: start now with 3.3.2, update if there's a 3.3.3 that has bug-fixes you need, and focus on your game. If you succeed and complete it, you can consider 4.0 for your next project.