Should of will replace
should've, because that's how we pronounce it. Those who read text, especially more formal text or older works will see the should. have. connection earlier in their careers, and the knowledge of its origin will mean more to them. But children aren't likely to encounter should've until 4th grade (reading level) at the earliest.
Should of will be what they have heard all their lives up until that point and always retain some power.
In fifty years, bright children will encounter should've = should
have, not should
of, and have one of those lovely moments of epiphany "Oh, that makes much more sense. I see where that comes from now!" But it will be a curiosity, not a form that one changes to. The rest of the world speaking English will only accelerate that change.
Think not? Will he, n'ill he,
ne cest pas?
