True on all points. I also thought that they, theoretically if they are alive still, could be at some more distant refugee camp and Lona just never found them - with the chaos, separation and death during the Sybaris fall in mind - Lona just does not have any reasonable basis to think that they are still alive.
At the end of day it all depends on Eccma and what he choose to do with it.
As a little sidenote: sure, if they were to be still alive they most likely would be in dire living situation. But at that point, at least on my playthrough, Lona is basically a killing machine which can go head-to-head with any enemy and has more than enough money to spare to, theoretically, take care of her family (i.e. put them on the ship).
i suspect a few things for them knowing how the creator works:
1. They both are dead and does not apear in the game
2. They are dead and we only see their corpses and maby a note/diary
3. They are alive but we see them die in a cutscene
4. They are alive and both are slaves
4.1 They both eventualy die being slaves
4.2 You could rescue both of them from slavery, what's next is umpredictable
4.3 Father eventualy dies being a slave but mother is alive so you can rescue her, what's next is umpretictable
4.4 the same as above but mother is the one who dies and father is alive
5. They are both alive but not slaves living in a really deplorable condition
5.1 Eventualy they both die pacificaly or brutaly in front of Lona
5.2 they do not die and you can escolt them to a save place
5.3 Something happens and father dies and mother is abupted to a rapeloop so lona have to saver her, what's next is umpredictable
5.4 Something happens so mother dies and father gets complety crazy and end being a companion (to help lona and revenge his wife) or a enemy (is so crazy that he tries to Kill or rape Lona so you have to kill him)
5.5 something happens so mother is abupted anyways but father is alive, you save her and the rest is umpredictable
6. You only find a letter what it say they are both alive and left the island leaving lona bahind
6.1 they leave without Lona because they think she died in the caos
6.2 they left lona bahind because they are terrible parents or do not care about her
6.3 they left lona in the island because the fortuneteller say so and they agreed because... some reason
6.4 only one of them find the way to leave, the other or die or is still in the island somewhere so one of the things above could happen
6.5 they just leave without Lona for no reason
What else do you think could happen to them if they appear or are mentioned again in the game?