Let the hive mind of Engadget get that for you.
"I've found myself using my PC for a lot of conversations lately, and I'm also considering recording a podcast to share with anyone who will listen. There are tons of USB headset / microphones out there, and I'm hoping someone has some solid recommendations based on experience. I'll consider both headsets and standalone mics, by the way, but I'd like to keep the bill under $100 if possible. Help!"
I can't see MS leaving the current 360 owners completely out in the cold (this isn't apple, where they want you to buy the latest/greatest in order to maintain your hipster card). MS will probably allow for some sort of upgrade path with the HD, but if you are really pinging for HDMI, you'll have to go with a new box. Then they can just nickel and dime you to death with the service, and other small items.