Samsung has released the update, but your carrier has to run the update through QA and release it themselves before you'll be able to install it via standard methods. Depending on your carrier, it may take a while (if you're on Verizon in the US, for example). Generally, carriers (at least in the US) don't provide specific info as to when updates will be released -- your best bet is just to check every now and then.
You will NOT need to be rooted to get the update, in fact, as several folks here have noted, you will most likely need to not be rooted to get it.
It depends. Sometimes if the only thing you've done is root the phone, OTA updates will still work. Sometimes they don't. Sometimes they attempt to install then fail then break stuff, remove root or simply brick the phone. I haven't tried myself or seen reports on this particular phone or update to say with any certainty what to expect in this instance.
If you've taken the time to root your phone, you should take the time to learn how to manage updates yourself, and in general you should avoid installing any OTA updates pushed by your carrier.
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