For present talk about the development of construction techniques and mechanization. For future you can talk about how many of the original traditions will remain the same, but the human construction will decrease, actually a pretty sad thing.
That's exactly what i mean. not many guitar's are completely hand made. Most companies use routers that make multiple bodies at a time. Most assembly is done by humans though. I am not really sure what else you could do other than construction techniques, maybe design of pickups or something and how that progressed. Maybe the developement of a dreadnought over o styled guitars. Honestly the main difference between an old guitar and a new one is experimental pickups versus a mass produced set and that the wood has aged and gained a better tone.
Ok I don't have to extend myself so much with present, I'm also going to mention the great ammount of guitar effects now a days and how guitars are used for special effects, now I need something for the future part.