RV770XT-based GDDR5 cards are barely going to make it for the 25th launch. We've learned from various sources that these cards will reach retailers literally just days, if not hours, before the launch.

Radeon HD 4870 cards are being produced as we speak, and we were told that there shouldn't be many shortages after the launch date.

You can be sure that you will get quite a lot of Radeon HD 4850 as of next Tuesday, but it might be tough to buy HD 4870 for the time being. We were also told that this situation will get better, as the cards are coming as of next week.