We have examples of outcomes of rewilding. We do not really have to speculate much. Take the European bison, which was even closer to extinction than its American cousin when it was saved.
A successful breeding program was instigated and the population has grown to more than 4000. They are all semi-tame animals, dependent on and accustomed to humans. They have been distributed to several countries, but there is little room for them in today's European landscape (the reason they almost went extinct in the first place).
So, every herd needs a reserve with appropriate habitat for wood bison, i.e. a forest with sufficient open spaces as well as large territories for old, solitary bulls. These can either be already existing reserves or reserves created specially for the bison.
As it turns out, the needs of the bison and interest in having them result in creation of wild areas that would otherwise continue to be farms and/or forests managed for timber. In other words: rewilded areas. Even though the bison are not truly wild, have a limited genetic base, a short natural history and are dependent on humans, their existence doubtless has positive outcomes for a host of species also found in the reserves, as well as feel-good effects on those of us humans lucky enough to have seen them.