Now, I usually do my very best to approach new features with a positive viewpoint at best, and an open mind at worst, but I really hope these come with the option to turn them off. I'm fairly confident that they will, but not 100% sure. I've spoken before about my dislike of additional sound feedback during PvP, hence why I don't use addons like GladiatorLoSSA. The visual clues do just fine for me, in both arenas and battlegrounds, and I am of the opinion that audio is best used to hear spell effects and communicate with my team, so I am not really keen on these!
But, on the other hand, I know that many people are big fans of audio announcers. The aforementioned GladiatorLoSSA wouldn't be so popular and highly recommended otherwise! I remain excited to see just what other UI changes Blizzard are planning to bring out with 5.1.