The new RV670 revision A12 will make enough space for a new version of 3870. The new Radeon 3870 with revision A12 chips will work at faster clocks and should score better than existing cards.
The other thing that we can report is that it is expected in April to May time frame, which clearly indicates that the R700 family will launch a bit later than that.
The story behind the RV670 chip is that the current A11 revision that was launch back in November was not supposed to be the launched, but it was the first A11 silicon that ATI managed to ship. Usually by ATI, A12 silicon is the launched one, but for a change something went well in DAAMIT.