Fully agree with your second paragraph!
As for the first, I would be surprised if your brother really believes he can drive the price. He likely produces commodities (unless he is vertically integrated and processes and direct markets his product). That means that eventually the price moves to the average cost of production and the people who profit at that point are the ones who are able to produce at a cost below average, and normally at a greater scale and efficiency. I strongly suspect your brother either knows this and is confident he can compete, or has a different business model that somehow insulates him from these realities. And he may not be explaining that to you, or you may not be hearing his explanation.
The beef industry is currently enjoying a super cycle hitting at the same time as the regular 11 year cycle.... So along with the past few years of record high feed prices, thus huge increases in cost of production which along with a couple severe weather issues, caused a large sell off of brood cows and cattle in general..... This has all created an inventory of cattle (at least beef cows) which is at something like a 55 year low. And now in the past few months, corn prices have dropped severely and cattle guys are very profitable again... Thus the cycle will turn as profit causes an increase in supply. So you are completely correct in saying "no" his profitability is not guaranteed..... And yes there is some switching to chicken, just go out to eat and look at a menu. However pork has it's own challenges! Go price bacon. Chickens have a much shorter life and generation cycle so they can respond much quicker... Turkeys as well... In fact there are new turkey barns being built as fast as they can. Don't think sea food is endless either......
This all further proves the point that capitalism works, and the RSA saying regarding wildlife is correct..... "if it pays, it stays!"
There is a reality that more and more people around the World are entering the middle class and the first thing they do is to put more protein in to their diet (meat, cheese, soy, fish). Then they buy clothes (cotton), go out and have a beer, wine, or drink of some kind (barley, hops, grapes, grains in general), they also get pets... Especially in China where there are basically no siblings AND no cousins... The kids need a pet to play with! Well the pets eat... Add in ethanol which in the USA now takes more corn than livestock does..... What this all has in common is a much greater need for farmers to produce more. Add in a projected population growth to something like 9.2 billion within the next 50 years (at which point it is expected to level off and even back down a bit)...... Think this will affect wildlife areas in Africa???? Elsewhere?
There is good news in all this, there are many areas where wildlife may be the best use of resources to produce more protein.... Perhaps eland will supply part of the meat... And maybe it will continue to be blesbuck, springbuck and gemsbok. Some of these species are better suited to turn available feedstuffs to protein than cattle or other domestic livestock. I do think it is obvious hunting can take place on the same properties that commercial culling operators go in to harvest that protein. And modern agriculture can produce a lot more from less with technological advances. If permitted. The reports I see say we can maintain most wild places and still meet these increased demands. However I'm sure more areas of Africa will be pressured towards human needs.