Update: Even more DLC was put up for sale today on the Xbox Live Marketplace, including:
“OMG” by Usher ft. Will.I.Am, ‘Umbrella’ by Rihanna VS ‘Let’s Get It On’ by Marvin Gaye, and ‘Shutterbugg’ by Big Boi ft. Cutty VS ‘Return Of The Mack’ by Mark Morrison.
The DLC is available for 640 MSPoints (or $7.99)
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Activision has released the first pack of DLC for DJ Hero 2, and it is available for 480 MSPoints (or $6.00). This extended mix contains the following:
“All Of Me†by 50 Cent featuring Mary J. Blige vs “Radio Ga Ga†by Queen and “DARE†by Gorillaz vs “Can’t Truss It†by Public Enemy
Also, it appears that the DLC will work on both DJ Hero and/or DJ Hero 2. If anyone purchases this, please make sure to let us know if it was worth the money or not.



[...] See the article here: DJ Hero 2 Gets First Dose of DLC [...]
I have already purchased this and the release date is October 29, 2009. I think they just made some DJ Hero DLC compatible with DJ Hero 2.
The Extended Mix Pack 01 came out a few days ago (as you said on October 29), but the Hit Makers Mix Pack came out today.