Why are they still developing EU4?

[Johan]

I don't believe I've ever seen the devs say something like that around here. What I have heard them say is they won't make a sequel just to make a sequel but rather because they have ideas for improvements they can't execute with the current game.

As for the original question; why wouldn't they? Unlike 99+% of other games out there EU IVs active player base is still growing after all this time. At the end of the day they're a business and it's not good business to just turn your back and walk away from servicing a growing market...

I am pretty sure I've said that we would continue to support a game as long as its profitable to do so. That has no major correlation with when a sequel is created or not. iirc, CK3 had been in full development for over 3 years when Holy Fury was released.