Will there ever be new musical instruments?

I know it may sound stupid but I have always wondered this: why do musical instruments basically stay the same in their basic design throughout time? Guitars, drums, keyboards, etc. I am NOT talking about the performance of each instrument (it is pretty much clear that instruments become more and more efficient throughout time). I am talking about the design, the shape. Have we reached the summit of musical instrument design? is that why guitars (for example) will always be shaped the way they are? Are the instruments fully ergonomic and so they are now destined to stay unchanged until our human body changes? Will we see rock bands in the year 2500 still playing the same kind of drums and guitars that ALL bands still play (guitars hanging from their necks with one hand on the "neck" and the other on the "bridge", or banging circular drums with sticks)? Will instruments ever change their shape significantly? Have we invented all musical instruments there can ever be invented?