I am someone who has done some work on Godot 4 and Godot 3. There is quite a lot of changed syntax, so I will say that a game that has already started going will have a lot of code rewrite, even though a lot of it will function about the same. It is quite painful to do a large amount of adapting at this point, considering how far along this project is. Not saying it is impossible, but it is absolutely time-consuming.
Good luck in whichever route you will decide to take.
Viewing post in Identity: Version 0.3.14 – Public Release comments
Hello there!
It is always nice to see fellow programmers. While it is true that a lot has changed from Godot 3 to 4, it also has several things that at least, I personally, consider essential for a text game, such as improved BB-Code.
On the other hand, the Godot 3 VN-framework for our game wasn't written by me. Having to fix the existing framework will amount to about the same kind of work given that I'd need to shoehorn solutions and further study code that somebody else wrote.
The main things that we need to port over (which are also almost finished) are the animations, and windows. But, everything else, like the text logic, saving, loading, image logic have to be rewritten from the ground up, anyway.
I would say I am about 30% done, but it is very time consuming as you said. It wasn't an easy decision to make, but recurring bugs are a persistent thing that players report. I would rather just fix the bugs than have fans put up with those bugs to enjoy our game.
Thank you, and I also wish you luck in your endeavours!
Baku