When everyone stops eating meat and turns to "healthy" meals like corn based vegetarian burgers I think we are all worse off.
Variety, locally grown produce, locally raised animals is the best way to keep diversity and quality. The vegetarian food available now is good because it's not as mass produced.
It's also not the point of ecological vegetarianism: it's preserving the diversity of natural ecosystems, as opposed to food farms.
While I don't have the numbers, I strongly suspect there's not enough grass to feed all the humans the amount of meat they would like to eat right now. At least based on observing the prices of intensive vs grass fed, or watching the numbers for intensive production alone.
So if we want grass fed as the new normal, we're either going to have to intensify it back again, or we'll end up eating respectively less meat. That's near-vegetarianism or bust.
The solutions to let the market solve the problem - if there was only grass fed meat available the cost would be very high and meat would become a luxury again.
The gotcha is mainly that one can support the welfare of animals but also be ok with their systematic extinction. I don't know which outcome is worse.