Come visit the forests in Western Kansas where they had to clear-cut thousands of acres for the dairy farms and cattle feedlots. (sarcasm as there's probably an average of less than 100 trees per square mile here).
This is worth pointing out; a lot of the lands used for grazing simply aren't viable for much else, and thus we couldn't really plant anything else there.
I suspect on average, we will eat less meat in the future, but that we won't get rid of meat totally simply because it's the only way to get food from some areas.
> a lot of the lands used for grazing simply aren't viable for much else, and thus we couldn't really plant anything else there.
Perhaps in the some places, but 80% of deforestation of the Amazon rainforest is for cattle ranching. [0]
Here in New Zealand, European settlers managed to clear 27% of all forest in just 10 years [1], replacing it with farming, which is what it's still used for (especially cattle, these days, and obviously they didn't stop clearing forests at 27%, they kept right on going). This is land described by early European explorers as "immense woods, lofty trees and the finest timber" [2]
Also, land doesn’t have to be productive for business. We could take the cows away from land that’s not viable for other farming and just let the land be. (My guess: given sufficient recovery time we might be surprised at what does grow)
Perhaps one day we will let those areas re-grow without interference again, but until we're past the expected peak of 12 billion people on this planet about 100 years from now, we're going to need every calorie we can get hold of to prevent mass starvation, considering we're also going straight into a top-soil crisis, depleting groundwater reserves by massive irrigation, and so forth.
But yeah, I was mainly referring to natural grasslands where the original grazers have been replaced by grazing cattle. De-forested land should be re-forested if it can't be used for anything else.
If you look at the above street views posted, you will see that the area surrounding the farm and feedlot are being used for grain. Also, note that those two operations are about 20 miles apart, with no other large cattle operation between the two (you can follow the street view and see for yourself).
The point is that Kansas is used largely for plant agricultural, and actually isn't wall to wall cattle production.
Dairy farm street view:
https://www.google.com/maps/@39.4449329,-100.8322638,3a,75y,...
You will notice the trees in the above view are clustered around the offices.
Feedlot street view:
https://www.google.com/maps/@39.9084198,-100.5339579,3a,75y,...