I doubt that. There are both men and women who prefer small.

What might happen, is that whatever cultural ideal becomes contemporary, is also what most people will opt for, but that won’t mean people on the fringes of the bell curve stop existing.

I find it more likely that if big breasts become “easy” to get, the ideal will simply shift to something else, as the rarity is part of the appeal.

If a trait becomes common, at least some portion of people lose interest.