Will the Apple Store replace Macbook Pro keys or other parts if serious wearing occurs?
Rather than ask us, you might ask your local store since they are the ones that will make the call.

My guess is if you have a functional problem where you loved the Mac to death and used it so much the keys are worn, they would replace it under AppleCare or the standard Warranty. I wouldn't expect warranty service for normal wear and tear and this will likely be up to them to make the call whether your specific instance is one or the other.

Also - do go in if you are frustrated with your purchase. Go now and not later, since the sooner you show them wearing, the sooner they can document it and it's more likely they'll want to replace something that is wearing out prematurely. Think like tires, if yours wear out in under 5000 miles (or km) it's clearly something the warranty should cover. Several years of wear isn't a defect in the manufacturing and just plain old you wore it out.