This would make some sense.

Last year there were rumors of "8970" bringing a "just 20% increase over 7970" and having roughly those specs.

And then we saw people like LordEC911 posting "They're shooting for 75% over 7970!".

Both were likely true. AMD may well have had the 28nm "20% higher" chip in the works, and the "75% higher" chip to compete with Maxwell.

When they were saying "No new high end this year" it was probably because they saw no need to launch the 20% higher chip figuring customers for $1000 Titans and 690s were a small group. The 780/770 launch forced them to resurrect the 20% higher part. (which could well have been done by now and just need to be produced and packaged)