Will or do social sites kill email?

One function email has certainly lost or rather keep loosing is keeping people up to date about your life - personal or professional. I mean before social media came into the play I used to write long emails about certain things which had happened in my life, now I can broadcast my personal events via FaceBook or Twitter daily / hourly. But there is other thing which social network sites simply can't kill - taking time. When you type a message on Twitter you unconsciously try to do it fast, of course - it's Twitter, it's about your life up to a second, you gotta to deliver your news fast :-) At least you think so. And there is other thing which is subjective, but in my opinion, prevents email from fading away near soon - an affection to your favorite email client, I simply love to compose emails in my Mail app on Mac OS! And finally - for now none of social sites allows you compose/edit/delete your messages offline, it's simply against their nature - they suppose to keep your messages in a cloud. I can't see the way how FaceBook or Twitter will get its own Gears app like Gmail has.