At the very least, the devs have stated that they wanted to add China. So either when CK2 becomes better optimized or computing power catches up to make it possible.
I kind of doubt that CK3 will happen at this point. There's too much built-up stuff that either CK3 will sell nothing at all for missing all the DLC features CK2 ended up with, or it will have them and Paradox won't have a way to sell more DLC. It's like WoW, no one asks when WoW2 is coming out.
I will make Sweden a feminist country with an all female council by the year 900. I will be remembered as the most progressive ever!
But that's haram! How can you be progressive by shutting out the religion of peace?