It looks like the rumor going around the pre-CeBit floor is that AMD and its partners will be showing off a GDDR4 version of the recently released Radeon HD 3870 X2 card (review here).  The current cards use GDDR3 memory but there are not as of yet any indicators that performance will be increased because of it – stay tuned!
Most of ATI’s partners will showcase their Radeon 3870 X2 DDR4 versions of the cards at Cebit. For a few of your that might not know, Cebit starts on the March 4th, so on the coming Tuesday and it still remains to be the biggest computer tradeshow. It takes place in Hannover Germany.

Radeon 3870 X2 with GDDR4 and some water cooled cards will be the top of what ATI partners have to show and we also learned that the production of GDDR4 X2 cards should start in the middle of March.

The cards should be available as of first week of April and they tend to be a bit more expensive but we don’t know how much.

Don’t expect a big performance increase out of these GDDR4 powered cards but they will be a bit faster than the currently available GDDR3 3870 X2 cards.