Farmland isn't going to be developed for the same reason it's not currently being developed, it's either zoned so development is difficult, or too far from the city to be interesting for development.
Also, unless we figure out how to replace all crops with vertical efficient farms, demand for agriculture is going to remain. It will just shift to different crops which can't be farmed this way.
Also, unless we figure out how to replace all crops with vertical efficient farms, demand for agriculture is going to remain. It will just shift to different crops which can't be farmed this way.