Would be a very nice addition! A chance to get to know people via voice chat seems ideal for the social game Destiny is trying to be. I do however like the whole Journey (the game) thing it's going for as well. With silent guardians coming in and out of your adventures has a certain charm to it in my own opinion. All in all a proximity voice chat, with an on or off option, couldn't hurt the game. Cheers!
Thank you for your feedback and support!