The planned scope of Chapter 3 will almost certainly be as big as it gets, for practical reasons. Part of the reason 3 has taken so long has also been constant distractions and dramas in my own personal life as well, which the release of 3 will hopefully empower me to diminish greatly. Mo' money, LESS problems in this case. But it is also just a very big game.
The first game was "Let's see the bare minimum I can make and still have something fun". The second was "Ok, I have SOME time and budget, let's try to make something decent in terms of scope." 3 has been "Let's see how far we can reasonably push things". So for 4 and 5, I may actually pull back a little. But we'll see. Each one is a learning experience in its own way.