I just spoke with Raja Koduri, the new head of graphics hardware and software development at AMD, who recently returned to the company after some time away. Koduri, incidentally, spearheaded the development of the original CrossFire implementation way back when.
In our talk, Koduri acknowledged that the frame delivery issues with CrossFire were "unfortunate," and he expressed a desire to make things right. Koduri told me AMD is working on a fix for CrossFire and single-large-surface display configurations, like Eyefinity and tiled 4K monitors, for current Radeon graphics cards. He said AMD plans to deliver a driver with the fix this fall.
AMD's newest Radeon GPU, the "Hawaii" chip that will power the Radeon R9 290 and 290X cards announced earlier today, will of course be a top priority, as well. Although we can't yet divulge too many details, we expect Hawaii-based graphics cards to arrive with a very capable solution for CrossFire frame compositing and pacing already in place.
Some of the new Radeon cards announced today that are based on older GPUs like Tahiti and Pitcairn will presumably have to wait for the fall driver release in order to see this issue resolved.
The good news is that AMD appears to be very much aware of the importance of resolving CrossFire frame delivery problems, and they seem to be confident that a satisfactory fix is possible within a relatively compact time frame.