Depends! Increased density should drive up the price of land.
However, if you are in a neighborhood of single family homes and a huge multi family building is constructed on your block, your home price will go down because there will be enough supply to meet demand, taking pressure off the single family homes.
If you are in an already dense city and regulations are relaxed so that more high rises can be built in more neighborhoods, the price of your condo all else being equal will be lower because there will be more supply. The land price may well go up but your individual apartment would likely be worth less.
a huge multi family building is constructed on your block
which is why NIMBYs should at least be in favor of gentle density - duplexes and triplexes, small walk-ups, etc. But they fight those like the end-of-days too.
However, if you are in a neighborhood of single family homes and a huge multi family building is constructed on your block, your home price will go down because there will be enough supply to meet demand, taking pressure off the single family homes.
If you are in an already dense city and regulations are relaxed so that more high rises can be built in more neighborhoods, the price of your condo all else being equal will be lower because there will be more supply. The land price may well go up but your individual apartment would likely be worth less.