If all natural meat consumption stopped tomorrow, Brazilians would cut down forests to grow whatever is needed for fake meat. The problem is land is one of the few economically exploitable natural resources the country has to sustain itself.
https://www.entegra.com.au/anna-creek-the-biggest-cattle-sta....
Australian beef is some of the highest quality in the world, and it's almost solely raised in areas that have very low impact on the environment. (Dairy farming is different, of course, because the location of dairy farms is important to have a close proximity to the dairies and thus the consumers).
But unfortunately a lot of people view the US agriculture system as the be-all and end-all, and don't look to the rest of the world that can actually perform fairly low-impact agriculture.
Plant based meat uses less resources than beef so I would call that a win in my book.
If you tell an Iowa corn farmer than he can't grow corn anymore, he doesn't just give up and let his land turn in to prairie. He will grow soy, or raise pigs, or whatever else monetizes the land.
Brazilians will keep cutting down forests because they depend on the land for income. They ultimately don't care what the deforestation is for, only that it feeds their family.
I don't know what they'll do with the areas already cleared but there wouldn't be an economic incentive to cut down more forest.
This study about soy in the US and Brazil that was posted a few weeks ago is quite interesting about the link between deforestation, soy and livestock (https://ourworldindata.org/soy)