On the contrary, if technology continues to improve exponentially as it does today, it is far more likely that in the future we would be terraforming other planets and populating them with more animals, than it would be for your darker future to pan out.
I think paleo, and Primal Blueprint, would be much more effective and healthful, if people generally ate more vegetables. Mark's Big-Ass Salad is an appeal to this concept, but seriously, how many people do a BAS every day and how many of our BAS' are loaded with a wide variety of fresh veggies? Sourcing quality, fresh veggies every day is hard work. Unless you have access to a daily salad bar, most of us probably aren't getting all the veggies we need. Then when you throw in the fact that veggies need to be prepared in meticulous ways to match the nutrient and vitamins contained, it makes it even more difficult--some veggies are best steamed, some roasted, boiled, juiced or raw.
I think if somebody could put together a really awesome vegan diet, and then add some meat, you'd have a helluva diet there!
If I had somebody fixing me a couple of big-ass salads a day, and vegetables and fruit, I'd be eating mass quantities, for sure.
It is the nature of life to evolve. You are suggesting we go against that core function of life. If life on earth has any hope to survive the ultimate death of the sun, it will have to advance beyond a society that requires raising animals to slaughter for energy.
Chances are that you will not know the difference between invitro meat and organic meat unless it is labeled.