Genes are actually a lot more complicated than we know about them right now. Sure, you can splice certain genes into an organism, but considering one gene can code for everything between hair color and penis size all at the same time, it takes a lot more than just plopping the gene for wings into a human and voila.
Personally, I think we might figure out how to turn our arms into wings, but considering we would also need hollow bones, less muscle, and less fat to actually be able to fly, we would probably resemble birds or some really ugly scraggly looking creature with an oversized head, which would kind of defeat the purpose of getting a human to fly.
The whole question revolves around what you think a human is, and if after all those genetic modifications, whether they are still human or not. Because if you're changing so many human genes into bird genes or something, would we be birds or humans?