It’s a false dichotomy, leave them on farms or leave the in the wilderness to die. Sanctuaries treat cows with dignity instead of objects for profit.
There will be more cows existing at any one point in time if more people don’t go vegan because of the population increase. It would take less resources to let the cows alive now live out their natural lives and there not be any cows anymore in 20 years than to continue sexually abusing them, forcing them to reproduce, then killing 30 million of them a year in the US alone. There’s 91 million cows in the US right now, it would take less resources to let them live out there lives and there be no cows in 20 years than if there are over 91 million cows in 20 years. The population will decrease from 91 million down to around 0 in 25 years whereas if people keep eating cows, there will be over 91 million cows consuming resources in 25 years.
This utopia scenario is a fantasy, but it demonstrates an important fact that if we breed less cows, less resources will be used and there will be less of a toll on ecosystems. The ways less cows will exist is if humans stop reproducing as much and/or go vegan. The numbers will decrease gradually the more that people go vegan.