Skull Face explains his plan in the jeep scene. It has two parts.
One is to eliminate the English language through the vocal cord parasites. He wants to eliminate English because it's the dominant language. He has a problem with Western cultural imperialism, how the English language (and thus culture, and thus how people see the world, right and wrong, etc) is squeezing out minority languages (and thus their cultures, etc). The most pure expression of this problem is the Patriots. Skull Face knows Zero can't continue to impose his will on the world if English is gone, since the Patriots will depend on this lingua franca for unification and control.
The second part of Skull Face's plan is to make sure that the languages/cultures that remain will respect each other's boundaries. He will sell Walker Gears (which can be equipped to fire nukes) and homegrown nukes (made with metallic archaea, so no processing plant necessary) to every government, PMC and terrorist cell in the world. He will use Sahelanthropus to inspire fear in the general public, escalating the Cold War. Everyone will buy Walker Gears and nukes, and since even the smallest group of people will now be nuclear powers, the idea is nobody will fuck with anybody.
In other words, it's the theory of nuclear deterrence — Mutually Assured Destruction —applied to every single organization on earth. It's no longer just the big boys who will have the nukes. Now no one will be able to walk over anyone else. The languages/cultures that remain "after English" will fall into a certain balance where they "respect their neighbors," as Skull Face says in the speech.