They will 'kind of' win, as in meat taken from slaughtered animals will, most likely be grown in labs instead (Though, as The E points out, we are actually a fair distance from creating and accepting that kind of product). It's certainly possible that sheer weight of need will, and does, force farming away from the more area-dependant techniques, such as crop farming and livestock, and more into things like Hydroponics and GM. But that's not truly a 'victory' for PETA, it's not been done for ethical reasons, it's not that we are concerned about the animals, it's that we are concerned about ourselves.
Fact is, whilst there are people who choose to be vegetarian, the vast majority of humanity eats animal life, whether it be insects, rodents, bovines, equines or any other type. Indeed, there's growing arguments that 'insect farming' may be another route to dealing with the resource problem, so I don't see PETA ever really succeeding in stopping humanity eating or exploiting animals.