It seems that in the HP world, the ability to perform magic is some sort of genetic mutation. Now if they would only get together with a Muggle geneticist, it would undoubtedly be found out how to manipulate the genetic code, rendering everyone who could afford such medical intervention the ability to choose magical ability for their children. But, yes, like the genetic testing we already have, and the fertility drugs, it would only be available to the rich... or those willing to go heavily into debt.

As to magic in the real world, I think we call "magic" the processes that no one understands... not even scientists. I mean, very few of us understand electricity.. how a television works... how the internet works... but we use it every day regardless. The thing is, someone understands it... has the specialized knowledge required for it. So the thing is deemed "science". But if no one understands how something works, then it is magic... or a miracle, which is pretty much the same thing.