I think this is a relatively sensitive subject for Aikido, since it is relatively new and we'd all (well, most of us) would like to see the art preserved, we try to stick to "O-sensei's Aikido" in order to preserve his memory.
I can imagine the striking arts such as karate, okinawa-te, etc. have changed plenty over the years. From what I've read, jujutsu has too- the sengoku jidai would be an example- jujutsu involved a lot of tantowaza, which meant getting your opponent off balance, and stab him in a weak point of the armor.
My opinion: change with the times but also stick with tradition... as redundant as that sounds...
See ya in Aiki-Hell,