Given the current pacing, I expect chapter 4 will not be out for some time, but I also doubt it will be the last update. Because there are a TON of new scene hooks (that go nowhere atm) included in the game show that at HP has been providing the artist plenty of plot to make scenes for. (HP if you want to practice your pixel art / get bored while your artist catches up once you're done, adding more pixel anims for the roaming scenes would be kinda neat. They're unsatisfying on their own, but the ones you've paired with a CG are a nice touch).
Here is the current list of scene hooks that do not have scenes / cgs yet. Some of these are pretty easy to miss, if you found something I missed, let me know.
In the 1st town -
The king slime defeat scene doesn't have a cg yet.
There is not a continuation of the bridge soldier's blackmail yet
Roaming -
Sana talking to garret about more spell training - no progression yet
Sana having a date with / getting drunk for a mercenary at the inn. No progression yet.
Sana is seen with a guard in the bottom right portion of the market
Sana can be seen getting chatted up by a guard at the top right of town - no progression yet.
Sana gets invited by an adventuring party in the guild hall - no progression yet.
Sana seen surrounded by men at the top left of the market area (past bread seller) - no progression yet
In the 2nd town
The trainer scene does not have CG yet, nor a followup
The swimsuit roaming scene isn't finished yet - there are additional cgs in the files already posted yet to be added, possible variation for higher lewdness? And this is one that could really benefit from one of those pixel anims to go with it.
There is no continuation with the mine workers yet
I'm guessing that tower to the north after leaving town to the east is related to a sidequest?
Roaming -
Sana approaches a serious man outside the bar - no scene yet
Sana appears nude in the top left corner with fief - no scene yet
Sana has no progression with the pickup adventuring group yet
Sana talking to the meat market girl - maybe the market girl slips her a special sausage? I know this one is a bit of a stretch, but the author mentioned futa content planned, so a fox lover can hope.
In the 3rd town
No cgs for the orc captures during sneak section yet
The rest of the chapter 3 main dungeon content
Roaming -
Sana plays strip poker with a group in the shortstack elf cafe, no scene yet
Obviously there's other planned content besides this, like I'd guess the other towns will have a sidequest or two like the first town does, but this is what is actually teased in the game so far. This is just what you have to look forward to for the next major update (if the dev decides to continue a larger update strategy, hopefully - drip feeding tiny updates will only get more spam whining from certain types, larger ones give people enough to mull over of being done in ten minutes and back to whining).
As for gameplay elements - a lewd meter and stat tracker are staples of the genre, but what I'd really like, given all the roaming scenes and the hundred laps of the towns I did finding all the stuff in this post, is a feature found in the current version of Busty Priestess Sana by breast mafia - there is a key for advancing time, that could skip sana around town / advance a scene so I don't have to do so many laps.
As for estimated wait times -
So the game will probably still be in dev for a year at minimum, given a rough estimate of 6 months to get chapter 4 in basic playable shape, and 6 months for finishing the rest of the teased content - if each chapter aligns with the amount of content expected from town 1 and 2 (or expands, as corruption games tend to get more quantity of scenes later in game), finishing the expanded content will be bigger than an individual chapter update.
So for those who want to wait until it is actually finally done / has a significant amount of new content, or at least get some control of yourselves (looking at you obsessive "WHEN IS IT WANT IT NOW" spam types") I'd suggest a calendar reminder and bookmarking the thread, and ignoring it for a while.