[Tiktaalik]

Not necessarily true. An upzoning will likely increase the value of the land, which will result in higher property taxes (assuming this is a normal city with no prop13 nonsense).

The higher taxes could effectively force a land owner to sell their property.

Often part of what existing land owners are fighting for is preferential zoning which artificially keeps the "highest and best use of land" a low density detached house, which keeps land values relatively low.

[RhodesianHunter]

This is assuming no or poor homestead exemption.