ATI is working on a new revision of its Radeon HD 3870 X2 card and if all goes well, you should be able to get one by the middle of Q2 if not even earlier.
The new card will have an updated PLX bridge chip that will support PCIe 2.0 and at the same time, ATI is trying to shorten the PCB and add GDDR4 to the card. The current Radeon 3870 X2 has a PLX chip that supports PCIe 1.1 communication and obviously, a new card should have some better results with the faster inter-chip communication.
The RV670 chips will upgrade to revision 12 and this can probably means a higher frequencies and more performance. The current Radeon 3870 X2 dual chip cards come with RV670 chips revision 11.