My father-in-law hasn’t given us the land as promised

We have been married for eight years. My wife has a younger sister, and soon after we got married, my father-in-law informed my wife that the family owned three plots of land. He said that in the future, one plot would be given to my wife, one to her sister, and the third, where my in-laws resided, would go to whoever decided to live with them in their later years.

At that time, we were employed and renting a home in the city. My wife shared her father’s plan with me, thinking that we could sell the plot once given to purchase a home in the city.

We were young and newly married at the time, not particularly focused on real estate, so I did not give it much thought. Eventually, we took out a bank loan to buy a small, lovely apartment in the city, which I was confident we could handle.

Recently, I discovered that my father-in-law sold one of the three land plots to cover his personal expenses. Since the land was in a rural area, it wasn’t very valuable, and after settling his affairs, he gave his daughters a few million dong each (VND1 million equals US$39).

This reminded me of the earlier conversation, and I questioned my wife about what happened to the plan of allocating each daughter a plot. My wife seemed unsure as well.

I suspect that my father-in-law might have spoken casually and wasn’t serious about his promise. If he were, why didn’t he distribute the plots earlier so his daughters could plan accordingly?

Perhaps as a son-in-law, I shouldn’t concern myself too much with my wife’s family assets, but I believe promises, especially those involving money and land, should not be made lightly or just for the sake of conversation.

Am I right to think this way?